Police sealed off part of Capitol Hill today after reports that gunshots had been heard in the garage of a House of Representatives office building.

The shots were heard in the garage level of the Rayburn building, which houses offices of members of the US House of Representatives.

Bill Pickle, the Senate Sergeant at Arms, told Reuters: "We have been told by staff of shots fired and the smell of smoke in the lobby of the Rayburn House building." Mr Pickle said that there were no reports of any injuries.

Peter Hoekstra, a Congressman conducting a House Intelligence Committee hearing, interrupted a witness to request those attending to remain in the room and said that the doors must be closed.

"It’s a little unsettling to get a BlackBerry message put in front of you that says there’s gunfire in the building," he said.

The House was adjourned for a US holiday weekend and Mr Hoekstra’s committee meeting is the only business known to have been in progress. The Senate remained in session without interruption.

At the same time, Capitol police went room to room in at least parts of the Capitol advising staff to stay in their offices, according a House aide whose office was advised.

"They want us to stay in our offices, and I’m perfectly happy to do that, but I don’t feel endangered," said Gene Smith, chief of staff to Howard Berman of California, whose office is in Rayburn.

"They said they heard gunfire in the Rayburn garage, but this is a huge building," Smith added. "I’m guessing it’s a car backfiring or balloons popping."

A spokeswoman for Capitol police said: "At 10.30am we received a report of shots fired inside the Rayburn building. The information came from a call-in. We have many tactical units inside the building. The entire Rayburn building is being searched and that includes the firearms range there.

"We have no reports of anyone being captured, or of any injuries at this time. Part of the search includes looking for anyone who may have a weapon.

"Right now we want to err on the side of caution. If we have a gunman in the building, we want to find him."

The fleet of ambulances parked outside the building were there as a precaution, the spokeswoman added.

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