The United States Capitol Police is responding to reports of a possible explosive device in a truck near the Library of Congress, law enforcement officials said.
People in and around the Cannon House office building have been evacuated following concerns about the suspicious vehicle, which is located near the Capitol and the Supreme Court.
Police said investigators at the scene were working to determine if the device was an operable explosive and if the man in the truck was holding a detonator.
“This is an active bomb threat investigation,” police said on Twitter.
The man inside the vehicle had said he had an explosive, but this has not been confirmed, according to an official.
Congressional staff at the Cannon House office building have been relocated to the neighboring Longworth building, and people have been told to stay calm and use the underground tunnels to leave if necessary.
The Jefferson Building of the Library of Congress was also evacuated, while those working in the nearby Madison building were directed to go into their offices.
The area was blocked by police patrols and barricades, with fire trucks and ambulances at the scene.
The FBI and the Metropolitan Police of the District of Columbia are also involved in the investigation, with the help of the Bureau of Alcohol, Tobacco, Firearms and Explosives, which said it would send a bomb technician to assist police.
Officers said they are “responding to a suspicious vehicle near the Library of Congress,” adding, “Please stay out of this area.”
The FBI and the Metropolitan Police of the District of Columbia are also involved in the investigation, while the Bureau of Alcohol, Tobacco, Firearms and Explosives said it would send a bomb technician to support the police.
The White House said it is monitoring the situation and receiving updates from law enforcement.
There were far fewer people in the Capitol area than usual because the House and Senate are currently on vacation.
The incident comes months after pro-Trump protesters stormed the U.S. Capitol and two homemade bombs were discovered outside the offices of the Republican and Democratic national committees.