on the new theft that's been leveled against the united states. as the clock runs down to the anniversary on sunday, police, national guard, bomb-sniffing dogs are all out in force in new york and washington, d.c. intelligence officials are pouring over the names on flights from abroad. and abc news has learned new details on this threat. abc's brian ross has been talking to intelligence officials all day and he is standing at one of the many police checkpoints all over this city tonight. brian? >> reporter: gooooevening, diane. abc news has learned new details of the source of this troubling information. my colleague martha raddatz reports, the source, overseas, is well-known and trusted by u.s. officials but that in this case, his information about the vehicle bomb plot may be, at best, second-hand. even so, officials say at this point, they have though choice but to act as if the threat is real and that the clock is ticking. it was only 48 hours ago, on wednesday in pakistan, that officials say the cia developed the information. three men, including at least one american citizen, had traveled to the u.s. in mid-august, from pakistan, through dubai. a sign assigned to attack new york or washington with a vehicle bomb on september 10th, 11 or 12th. the information, very specific but still unconfirmed. >> it's uncorroborated. that means there's only the one source. none of our other sources are saying the same thing. and so far, we haven't been able to actually find any evidence in the real world that the report is true. >> reporter: late wednesday night, the intell jenls was related to washington and cia headquarters. early thursday at the white house, the president and the vice president received the first of several briefings on the threat. >> we don't have the smoking gun but we do have talk about using a car bomb. >> reporter: thursday night, as the president arrived to address congress, the fbi and the cia were in high gear. >> you use all the resources that we have. people are working 24/7 on this issue. >> reporter: late last night, the fbi and homeland security issued a bulletin to 18,000 local law enforcement agencies, detailing the vehicle bomb threat, including also small arms, homemade explosives and poisons. >> if you see something, say something. and that has always been true. and over the next few days, we should all keep our eyes wide open. >> reporter: at first light this morning, police in new york set up road blocks and traffic check points throughout the city. trucks passed through officers and cars with radiation monitors and other sensors, backing up traffic for miles. >> as long as we've been flying over the city this is about the worst that i have seen it. it is a nightmare. >> reporter: officials say if this threat is real, the three men likely came here with little more than clothes in a suitcase and an al qaeda formula for a truck bomb, involving chemicals easily purchased in this country, diane. >> all right, brian, thank you. and as we heard, intelligence officials are working 24/7 to put together the clues to follow the trail of the terror plot. and abc's pierre thomas has been in washington with them all day. >> reporter: at this secret location in the washington suburbs, every available analyst at homeland security's national targeting center is pouring over travel records of hundreds of men who entered the u.s. in august. they're looking at travelers from a number of countries including dubai, and the 250 flights that arrive to ameriric in that country every month. >> there are scores of people scrubbing through mounds of data, looking for potential leads. >> reporter: the names of those travelers are immediate lly forwarded to another top secret low kale. the national counter-terrorism center. analysts are hunting for the critical leads. are there connections with what's known about this plot? the analysts are running names through every u.s. intelligence terror watch list in a desperate effort to identify suspects. the pressure, tremendous. >> some people different go home last night, some people won't be going home tonight. in fact, i think this will run itself around the clock until they have figured out that they can stand this threat up, target those people and take them down or wash it out. >> reporter: the goal? use super computers to whihile down the huge list of potential suspects to a manageable number, as soon as possible, so each can be investigates. meanwhile, at the fbi, hundreds of agents in the bur rope's 50 field offices nationwide are on the streets, pressing informants about this threat and other intelligence. >> they can't afford to ignore any particular lead at this point. they know what's at stake. >> reporter: diane, here at fbi headquarters behind me, they remember the failures of 9/11. they're fighting hard to make sure it doesn't happen again. >> all right, pierre, thank you. pierre is on the case all night. and you heard mayor bloomberg of new york advise, in the face of the threat, be watchful, but don't panic. so, we wondered exactly what does that mean each of us should do? here's abc's jim avila. >> reporter: since 9/11, homeland security says most of the failed terrorist attacks on american soil have been foiled not by super secret intelligence agents, but by average americans. >> 70% of the detected terrorist acts in this country in the last ten years were detected by a citizen seeing something that they thought unusual. >> reporter: and this weekend, americans are on extra alert. >> i'm wondering if it's going to be safe to go out on ooept 1 seethe 11th. >> reporter: we went to bill bratton to find out what exactly we should be on alert for. >> you see somebody walking around the square that's all bundled up on an 83 degree day, that's somebody you might be a little mindful of. >> reporter: across the country saturday and sunday, large crowds are expected at college games and it is opening weekend for pro football. citizens should be on alert for someone taking pictures of sketching security devices. unusual interest in talking to stadium maintenance personnel or with questions about air conditioning and ventilation systems. at shopping malls this weekend, watch for someone who wants to get on the roof or for outsiders who have been paying unusual attention to emergency drills. multiple false alerts are a red flag, too. former chief bratton says in all these crowded places, families should have an escape plan. >> if something were to happen here, how do i get out of here? >> reporter: watch for delivery vans and trucks that don't deliver. they're just parked for long periods of time. and watch those trash cans. >> something that you might want to be cognizant of, somebody trying to stuff a very large package in there. >> reporter: americans on the lookout, on a weekend when everyone is the first line of defense. jim avila, abc news, new york. and now, we move on to other news of this day. president obama hit the road today to start selling his new plan to create jobs. he pressed the case for the $447 billion combination of tax cuts and incentives, showing up, in a sense, in the lion's den,n, at e university of richmond, home turf of an opponent, a key republican on this issue, house majority leader eric cantor, telling the cheering crowd to get behind this new bill. >> i want you to call, i want you to e-mail, i want you to tweet, i want you to fax. i want you to visit. i want you to facebook, send a carrier pigeon. >> we wondered, if the bill becomes law, how many jobs would it create? well, one private company estimated today, moody's, they put the number as high as 1.9 million jobs. and now to the flood zone across the northeast, a deluge from tropical storm lee, powerful enough to carry a house away in pennsylvania and smash it into a bridge. levees in wilkes barre are straining to hold back the susquehanna river. and 100,000 people along its banks have been forced to flee. and an amazing fact today from the weather service. lee dumped an estimated 45 trillion gallons of rain, from the gulf coast to new england. enough to fill yankee stadium up almost 58,000 times. and from a natural disaster to a manmade one. we wondered, how did a mistake by one repairman precipitate the biggest power outage in california history? power has now been restored to most of that stretch of california, arizona and mexico, where the lights went out on nearly 6 million people who live there. abc's abbie boudreau is in and yeah go. >> reporter: power has been creeping back slowly to millimeters of people today. the power grid is still described as fragile and the impact of the blackout stunning. traffic backed up for miles. all flights out of san diego grounded, leaving thousands stranded. beaches were still closed today after pumps shut down releasing more than 2 million gallons of sewage. it all started when one very unlucky electrical worker removed a piece of faulty equipment at a substation. that set off a series of outages, surges and short circuits that quickly knocked out one of two major trans mission lines, connecting san diego to the power grid for the western u.s. the second line, north of the city, was then jolted by the failure of the first and shut down, too. should it have made this huge of an impact? >> at the end of the day, one person making a mistake shouldn't have had this big of an impact. >> reporter: it has happened before. the northeast blackout of 2003, the biggest ever in the u.s. 55 million people out of power in eight states. at first, the thought was terrorists had struck again. but it turned out to be a tree branch that hadn't been trimmed, shorted out a sagging power line. an hour later, it was mayhem in manhattan. we may never know who that poor power company employee was who left millimeters in the dark last night. but we can only imagine he's wishing there was a tree to blame this time. abbie boudreau, abc news, san diego, california. and still ahead right here on "world news," jacaceline kennedy. the tapes she recorded, nearly 50 years ago. and the children, the babies of dads lost on 9/11, now almost 10 years old. what they see when they look in the mirror. copd makes it hard to breathe, so i wasn't playing much of a role in my own life, but with advair, i'm breathing better so now i can take the lead on a science adventure. advair is clinically proven to help significantly improve lung function. unlike most copd medications, advair contains both an anti-inflammatory and a long-acting bronchodilator, working together to help improve your lung function all day. advair won't replace fast-acting inhalers for sudden symptoms and should not be used more than twice a day. people with copd taking advair may have a higher chance of pneumonia. advair may increase your risk of osteoporosis and some eye problems. tell your doctor if you have a heart condition or high blood d essure before taking advair. if you're still having difficulty breathing, take the lead. ask your doctor if including advair could help improve your lung function. get your first full prescription free and save on refills at advaircopd.com. i see you're flatulent in three languageses graduated op of your gas. 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it's not my oral history. >> reporter: i think people are going to read w wn she said ablin don johnson and go, oh, my gosh. >> it't'funny, because she was really fond of him. she found him really amusing and warm-hearted. i hope people will listen to the tapes and then go beyond them and try to figure out what else is going into what's said. i think this is very much a moment in time. >> reporter: and so, from the kennedy library, where the tapes have been sealed since 1964, this coming tuesday night, they will finally begin to roll. we hear the ice in her glass, the sound of a match striking to light her cigarette. and in that voice, she tells her story. the witness to history, who made history herself. the young woman who fell in love with a man 13 years her senior. found her own voice andnd endedp writing a love story and chapter for america all her own. and again, make an appointment, tuesday, beginning at 9:00 eastern, jacqueline kennedy, her words, her voice, her extraordinary view of her extraordinary life. and coming up, what another first lady, michelle obama, says she hopes to be doing when she's 90. purina cat chow helps you well-being. we're all striving for it. nurture it in your cat with a full family of excellent nutrition and helpful resources. purina cat chow. share a better life. can collect on the surface of a denture. leading regular toothpastes are not designed to kill the bacteria that polident is designed to kill. polident's unique microclean formula has been proven to eliminate thousands of times more of the germs that can grow on dentures than leading regular toothpastes. that's why it's best to clean your denture by soaking in polident. not just once or twice a week, but every day. using polident on a daily basis will make sure that you are as confident as you can be in that denture. they want to see before they die. they don't fill photo albums with pictures from an online search. it's okay. the internet will be just fine without you. that's why we built the first search engine for the real world -- the dodge journey. and then we left three somewhere out there. if you can find one, you can have one. all you have to do is get out there. while i took refuge from the pollen that made me sneeze. but with 24-hour zyrtec®, i get prescription strength relief from my worst allergy symptoms. so lily and i are back on the road again. with zyrtec® i can love the air®. and now some moments in the news. first lady michelle obama stopped by the u.s. open today, part of her campaign against childhood obesity. she even hit a 55-mile-per-hour serve against serena williams. way to go. the first lady says she loves tennis, hopes to be playing when she is 90. so, she didn't pick up a racket until after law school because she said there were not many tennis courts in the neighbors where she grew up in chicago. and we don't know if these sneakers will ever hit the tennis court, but we have an update on the new nikes we told you about last night, based on the famous shoes from "back to the future ii," worn by michael j. fox. the first pair was auctioned off to benefit fox's parkinson's foundation. and they sold for $37,500. coming up, those baby, who look so much like their fathers, who never came home on 9/11. now 10 with a new message of love and life. do you have an irregular heartbeat called atrial fibrillation, or afib, that's not caused by a heart valve problem? 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>> should have had a binky. >> reporter: morgan rodriguez then -- this is so amazing -- and now, all grown up. still wearing her dad's firefighter medallion. that's great. you're going to keep that for life, i bet. >> this is kevin. >> reporter: and the toddler who told us -- >> my dad's name is kevin and i'm kevin. kevin kevin. >> reporter: this is kevin kevin now. and no one by one, they poured into the room, bringing the most precious possessions they have. dad's lacrosse stick. a biking jersey. >> i sleep with one of his shirts. >> reporter: why? >> because it just makes me feel good and safe. >> reporter: and what every child in this room told us, they treasure the most. someone tells them, of course, they're daddy's child. >> they say i look like him. >> they say he was free spirited and said that i was, too. >> sometimes i ask, does he look like me, she says yes. i look exactly like him. >> reporter: robert atwood was a firefighter. the thing that stays in your mind? >> his look. >> reporter: how do you mean? >> it's him, he has his hat on, ladder 21. he has his own gear, like when i go, when i'm trying to go to sleep. i look at the picture. and then i look in the mirror. it looks kind of like me and -- it's looking in the eyes. sometimes i have these dreams, like, lie when you bring a person back to life and then i wake up. >> reporter: they tell us, these reunions make it less lonely to be a 9/11 kid. >> i don't think i'd get along without these girls who help me, help me get through it. there's sean, me, and this is robin. >> reporter: and you're the bff what -- >> bff-wad. >> the best friends forever -- >> without a dad. >> i don't feel like i'm the only one whose had that before. these guys know how it feels. >> reporter: and for nearly ten years, you can hear them say it in this room. when you want to talk to dad, just look inside your heart. >> when you want to talk to daddy, you close your eyes and look inside your heart. where is your heart? >> oh, yes. that's nice, love. >> reporter: and remember, all the life he gave you is in your life to come. ♪ little voice came on the phone ♪ ♪ said daddy when you coming home ♪ ♪ he said the first thing that came to his mind ♪ ♪ i'm already there ♪ take a look around ♪ i'm the sunshine in your hair ♪ ♪ i'm the shadow on the ground ♪ i'm the whisper in the mind ♪ i'm your imaginary friend ♪ and i know i'm in your prayers ♪ ♪ oh i'm already there >> reporter: and so we choose the life of the children of 9/11. and george stephanopoulos and i and the abc news team will be there for full coverage of the ten-year anniversary of 9/11, beginning sunday at 8:00 a.m. easterer later that night, a special in primetime at 10:00. and we thank you for watching tonight. we're always there at abcnews.com. and don forget, "20/20" later. good night. mmm... it's fabulous food.