WASHINGTON — Police are responding to a claim of an explosive device in a truck near the US Capitol, according to law enforcement sources, and multiple buildings nearby are being evacuated.

"This is an active bomb threat investigation," the US Capitol Police wrote on Twitter Thursday.

Authorities on the scene are negotiating with the suspect, according to two law enforcement sources. The pickup truck the man drove to the scene does not have license plates, sources say.

A 30-minute video on Facebook was seemingly posted by the suspect, in which he speaks about a "revolution". The account on Facebook has now been shut down.

The White House said it was monitoring the situation and was being briefed by law enforcement.

Two Library of Congress buildings — the Jefferson and the Madison — and the Cannon House Office Building are being evacuated due to a suspicious vehicle in the vicinity, according to alerts sent to staffers viewed by CNN.

Staffers in the Madison and Jefferson buildings on Thursday were alerted by email to remain calm and relocate — and not to exit toward First Street. Those in Cannon were advised to relocate to the Longworth House Office Building using the Capitol's underground tunnels.

The Senate and House are not in session, and most lawmakers are not currently in their offices.

The Supreme Court has also been evacuated on the recommendation of US Capitol Police, according to a spokesperson for the court, which is closed to the public because of COVID-19.

The FBI said in a statement that its Washington field office's National Capital Response Squad is responding to the incident. The Bureau of Alcohol, Tobacco, Firearms and Explosives is also responding, the agency said on Twitter.

According to the FBI Washington Field Office Twitter account, the squad is working with US Capitol police and partners about a "suspicious vehicle and bomb threat near the Library of Congress."

US Capitol Police on Twitter Thursday said they are responding to the incident of a "suspicious vehicle" near the Library of Congress. "This is an active bomb threat investigation," the USCP wrote on Twitter. — CNN