A congressional office building near the U.S. Capitol was shut down for several hours Friday, as police investigated a report of shots being fired.
At about 10:30 Friday morning, Capitol Police issued a "shelter-in-place" order for the Rayburn House Office Building, just across the street from the U.S. Capitol.
That instructs anyone inside to move to the nearest interior office space and away from windows, and remain there until further instructions.
At the time of the warning, Congressman Pete Hoekstra was overseeing a hearing of the House Intelligence Committee. "I'd ask all members please, to stay in the room. There are reports of gunfire in the building," he said.
"Right now we want to err on the side of caution," said Sergeant Kimberly Schneider of the Capitol Police.
Throughout the afternoon, the building remained locked down as police and special operations teams carried out a door to door and floor by floor search.
Across the street, the U.S. Capitol Building itself was also briefly locked down, but re-opened a short time later.
Nearly five hours after the incident began, Capitol Police announced that their search had ended and the Rayburn building was again open for business.
Police attribute the initial report of gunfire heard to noise made by construction workers.
The U.S. Capitol and surrounding buildings have been the scene of numerous security alerts in recent years, some attributed to suspicious packages or substances, others to aircraft straying into restricted airspace over Washington, D.C.
Security has intensified dramatically since the September 11, 2001 terrorist attacks on the United States, and Capitol police routinely respond with maximum vigilance to potential threats.
In 1998, two Capitol police officers were killed by a man with a history of mental illness.