An accident involving asbestos work forced a temporary closure of the House side of the Capitol on Thursday and prompted House leaders to delay the day's session for two hours.
No injuries were reported. The incident occurred around 2:30 a.m. or 3 a.m., Capitol Police said.
A handful of workers were removing insulation containing asbestos from around pipes and valves on the building's fourth floor, above a staircase, said a congressional official who was not authorized to discuss the matter by name and spoke on condition of anonymity.
On-site samples and another sample analyzed by an outside lab revealed low enough asbestos levels that officials decided the building was safe to reopen, the official said. Those samples revealed levels similar to what is found in typical buildings in Washington, said the official, who did not provide any figures.
By midmorning, most of the building had reopened and Capitol tours on the House side had resumed. The Senate, at the other end of the 751-foot-long building, seemed unaffected by the incident.
The East Grand Staircase, which runs from the first floor to the third floor inside the House side of the building, was blocked off and more than a dozen workers and officials spent much of the day examining the area. Also closed was the Thomas P. O'Neill Jr. Room, a third-floor room near that staircase that was named for the late speaker and Massachusetts Democrat.
The House began the day's session at noon instead of 10 a.m. because of "an industrial accident," according to a statement from House Speaker John Boehner. Even so, by midmorning a handful of tourists was sitting in the visitors' gallery, observing an otherwise empty chamber.
The Senate began its session as scheduled at 10 a.m.
The office of the architect of the Capitol said in a statement that engineers and certified industrial hygienists had decided the building was safe to reopen and that the staircase would remain closed indefinitely.
Construction of the main, center section of the Capitol began in 1793 and was finished in 1826.
As the country grew and more lawmakers joined Congress, a south wing for the current House chamber and a north wing for the Senate were built. Both were completed in 1868, along with a new, larger dome.
The architect's office has been repairing decaying plaster throughout the building. It has also started preparations for a project to repair the 8.9 million pound, cast iron dome.
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