The police closed off several streets and sent alerts to congressional staff members, prompting evacuations.
WASHINGTON — The United States Capitol Police were investigating a “suspicious vehicle” outside the Library of Congress on Thursday, telling people to avoid the area.
In alerts to Capitol Hill staff members, the police urged some people to move inside offices, lock doors and stay away from windows, and told others to evacuate to designated assembly areas.
A man in the vehicle claimed to have a bomb, according to a law enforcement official. It was unclear whether he did actually have explosives.
The Metropolitan Police Department was “assisting with the report of an active bomb threat involving a suspicious vehicle, ” and “currently evacuating the area, ” according to a spokeswoman, Alaina Gertz.
The Capitol Police declined to provide details about the investigation and referred questions to the agency’s Twitter account , which urged people to stay away from the area.
With lawmakers scattered across the country for a scheduled August recess, most congressional staff were not on Capitol Hill when much of the complex went into lockdown. Many of the evacuated employees work for the Architect of the Capitol staff, building employees and workers helping with construction. And while thousands of people typically work in each office building, the pandemic has limited how many people were inside.
The Supreme Court building was evacuated shortly after 10 a. m., said Patricia McCabe, a spokeswoman.
As the police investigated, they shut down several nearby streets around the 100 block of First Street SE. Technicians from the F. B. I. and the Bureau of Alcohol, Tobacco, Firearms and Explosives joined the officers at the scene.
Just before 11 a. m., dozens of people flooded out of the Madison building, having been told by officers inside to leave the building.
“Everybody head south now, ” a Capitol Police officer said as other officers ushered construction workers away from work in the road and asked diners outside a cafe to leave their tables.
Ultimately much of the crowd, some carrying laptops and tangled handfuls of charging cords and headphones, ended up in a park near the building, calling family members and figuring out how to get home.
The threat unsettled visitors and employees at the Capitol, eight months after a mob of Trump supporters stormed the Hill on Jan. 6, in a violent attempt to prevent Congress from certifying the results of the presidential election.
After the Jan. 6 riot and the death of a Capitol Hill officer in early April, even the precautionary steps to investigate suspicious packages have become more intense for staff on the Hill, amid heightened security precautions.
Employees in the Madison building were notified of the possible threat through alerts, before officials came over the building intercom to leave the building.
Once on the street, employees were told to go home or head away from the complex, although some could not reach their cars and the nearest Metro stop appeared closed.
“They’re just being cautious — they don’t want to take hipóteses, ” said Paul Hines, a building services employee evacuated from Madison. Mr. Hines, livestreaming a news report on his phone, had left his phone charger, his lunch and most of his belongings inside.
“Wasn’t expecting this, ” he added. “I was about to eat my lunch. ”
Adam Goldman , Glenn Thrush and Nicholas Fandos contributed reporting.