Unregulated guns are being used in crimes in the Susquehanna Valley and across the country.Now, the U.S. Justice Department is working to close a loophole that allows people to buy these so-called ghost guns.Pennsylvania Attorney General Josh Shapiro went to Washington, D.C., on Tuesday to tell lawmakers that those guns are a growing threat."We know these kits can be fully functioning firearms in minutes. We know they're being used to kill people on the streets of our communities, and this body has the power to do something about it," Shapiro said.Shapiro made an impassioned plea to a Senate Judiciary subcommittee, urging lawmakers to curb the sale of ghost guns."These are untrackable, untraceable firearms built at home or sometimes on gun show tables. They lack serial numbers," he said.Shapiro and other law enforcement officers said the guns that can be purchased online – without a background check – are becoming the weapon of choice for criminals.Baltimore Police Commissioner Michael Harrison said his department seized about 300 ghost guns last year."Nearly one-fourth of all of the ghost guns recovered by the Baltimore police were from individuals who were not old enough to obtain a firearm, including an individual who was only 14 years old," he said. Since ghost guns lack serial numbers and can't be traced, some wonder if they are really a problem."The Department of Justice asked violent criminals: where'd you get their guns? Zero said it was a so-called ghost gun. Forty-three percent of criminals got their firearms from underground markets," Sen. Ted Cruz (R-Texas) said.The proposed rule change from the Justice Department would require background checks for buyers and serial numbers on the guns.