After several hours of investigation, Capitol Police in Washington D.C. lifted the lockdown that had been declared on the Capitol following a report that shots had been heard in the Rayburn Building parking garage.
The "shots" were in fact noise caused by repairs to one of the building's elevators, Army Radio reported.
Police had lined the street between the Capitol and the Rayburn building, rifles prominently displayed, and four ambulances were on standby outside the office structure.
The Senate was in session at the time, but the House was not. Most House members had left for a US holiday recess.
The Rayburn House Office Building was completed in early 1965 and is the third of three office buildings constructed for the House of Representatives. It sits across the street from the Capitol. The building has four stories above ground, two basements and three levels of underground garage space.
The US Capitol Police Department's Containment & Emergency Response Team maintains an indoor shooting range in the basement of the Rayburn building, according to the department's Web site. Eleanor Holmes Norton, the District of Columbia's delegate to Congress, raised the possibility that noises from a nearby construction site were mistaken for gunfire.
Within minutes of the reports, Rayburn's halls were virtually empty, and police were not allowing anyone to leave or take elevators or stairs to the garage.
At the Capitol, police quickly closed all doors, stopping people from entering the building. Tourists were herded into a first-floor chamber in the middle of the building. Other corridors on the House side of the building, where lawmakers had already left for the recess, were deserted.
The Capitol was reopened within an hour.