obama in his first visit to the u.s. since taking office. bp is under fire over concerns the oil giant helped with the release of the only person convicted in the attack. here's gloria riviera. >> reporter: as bp continues to battle an oil disaster of its own making, it is now also refuting accusations it pushed for the release of convicted lockerbie bomber abdelbaset al megrahi. in 1988, 189 americans were killed, 270 passengers in all, when pan am flight 103 went down in scotland. >> when you have such a horrific crime committed, you have to go the extra mile to be very careful. we want to know some of the details that are now being raised. >> reporter: congress is investigating whether bp pushed the british government to support al megrahi's release so the company could secure an oil drilling contract in libya. but in a letter to secretary clinton, the british foreign secretary wrote that the uk sees