The US Capitol was briefly locked down on Friday as police investigated the sound of gunfire in the garage of a House of Representatives office building, officials said.
The sounds were heard in the garage level of the Rayburn building, which houses offices of members of the US House of Representatives. The lockdown barred people from entering or leaving Capitol buildings.
Police said there was a firing range two floors away from the garage and the Rayburn building and tunnels below the Capitol remained closed during the police investigation.
Police planned a news conference for noon EDT (1600 GMT). Senate Sergeant at Arms Bill Pickle told Reuters there were no reports of any arrests or injuries though several ambulances were brought to the scene.
"We have been told by staff of shots fired and the smell of smoke," Pickle said. He later raised the possibility that a firecracker might have been the cause.
Rep. Peter Hoekstra, a Michigan Republican and head of the House intelligence committee, told an open hearing of the reports of gunfire.
Hoekstra's spokesman, Jamal Ware, said Capitol Police were monitoring the situation. "We have been asked to close the doors," he said.
Many members of Congress had left Washington, getting an early start on a week-long congressional recess. The House was not in session and the Senate was winding down.
Doors had been locked at the three large House office buildings and people were not being allowed to leave or enter the Capitol.