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Washington — The U.S. Capitol Police said Thursday it is investigating an “active bomb threat” near the U.S. Capitol after “responding to a suspicious vehicle” on Capitol Hill.

The agency said in a tweet Thursday the investigation is ongoing and urged people to stay away from the area. The suspicious vehicle is located near the Library of Congress, across the street from the Capitol building and Supreme Court.

At least one building in the vicinity was evacuated. An alert warned those in another building that is part of the Capitol complex and houses the Library of Congress of an “internal security threat” and directed staff to “move inside your office or the nearest office” and “stay away from external doors and windows.”

The Bureau of Alcohol, Tobacco, Firearms and Explosives is aware of the threat and responding. The FBI said its Washington Field Office’s National Capital Response Squad is also responding to reports of a suspicious vehicle.

The House has been out of session since the end of July for its August recess.

Jeff Pegues contributed to this report