Police are investigating a potential explosive device on Capitol Hill outside of the Library of Congress and have evacuated the area, including several buildings and nearby homes.

In a tweet on Thursday morning, U.S. Capitol Police said there was a “suspicious vehicle” in the area. Negotiators have been sent to speak with an agitated man in a pickup truck without license plates, according to CNN. 

“This is an active bomb threat investigation,” the agency said in another tweet. “We will update you all as soon as we have information we can release to the public.”

NBC News reported that the man was communicating with law enforcement using a white board from inside the truck.

Police are being assisted by the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and the Metropolitan Police Department. 

“They came pounding on our door,” Kathy Clark, who is visiting her sister who lives on the residential block right behind the Library of Congress, told HuffPost. “They said there’s a bomb threat.”

The incident comes more than eight months after a still-unknown individual placed pipe bombs outside of the the Republican National Committee and Democratic National Committee headquarters just a few blocks away on the night before the Jan. 6 riot.

Congress is not currently in session.

This story is developing. Please check back soon for more.