US Capitol Police are responding to reports of a possible explosive device in a truck near the Library of Congress, law enforcement officials have said.

People in and around the Cannon House Office Building have been evacuated after concerns over the suspicious vehicle, which is located near the Capitol and Supreme Court.

Police said investigators on the scene were working to determine whether the device was an operable explosive and whether the man in the truck was holding a detonator.

“This is an active bomb threat investigation,” police said on Twitter.

Congressional staff in the Cannon House Office Building have been relocated to the neighbouring Longworth building, with people told to remain calm and use the underground tunnels to leave if necessary.

The Library of Congress’s Jefferson building was also evacuated, while those working in the Madison building nearby were instructed to bar themselves in their offices.

The area was blocked off by police cars and barricades, with fire trucks and ambulances on the scene.

Officers said they are “responding to a suspicious vehicle near the Library of Congress,” adding: “Please stay away from this area.”

The FBI, the District of Columbia’s Metropolitan Police and the Bureau of Alcohol, Tobacco, Firearms and Explosives are also involved in the investigation.

The White House said it is monitoring the situation and receiving updates from law enforcement.

The House of Representatives and Senate are currently on break.

The incident comes months after pro-Trump rioters stormed the US Capitol and two pipe bombs were discovered outside the offices of the Republican and Democratic national committees.