A Maryland man has been charged with trying to bring a “ghost gun” into a House office building last week, CBS News has learned, the latest arrest involving firearms on Capitol Hill.

Jason White, 35, allegedly tried to bring the gun through a security checkpoint at the Cannon House Office Building shortly after 8:30 a.m. of June 24. The firearm was detected when White placed his bag through a metal detector at an entrance to the building, according to police.

The House was in session at the time, with lawmakers and staffers arriving at the Capitol complex for a series of committee hearings.

“There was no serial number present anywhere on the firearm,” according to an affidavit shared with CBS News. The filing said it had a barrel length of less than 12 inches and was “fully functional.” Ghost guns are typically made from kits and can be assembled at home, making them untraceable by law enforcement.