WASHINGTON (AP) — Police were investigating a report Thursday of a possible explosive device in a pickup truck outside the Library of Congress on Capitol Hill and have evacuated the area around the building, two law enforcement officials told The Associated Press.

U.S. Capitol Police said officers were "responding to a suspicious vehicle near the Library of Congress." The building is near the Capitol and the Supreme Court. Police have also evacuated congressional staff offices nearby, encouraging people to remain calm and use the underground tunnels if necessary to evacuate away from the area. Congress is on break this week. 

The law enforcement officials 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. The officials were not authorized to publicly discuss the matter and spoke on condition of anonymity.

The area was block off by police cars and barricades. Also responding were the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives. 

The incident comes months after a pipe bomb was left at the headquarters of the Democratic National Committee and the Republican National Committee in Washington a day before thousands of pro-Trump rioters stormed the U.S. Capitol in January.