Several Capitol Hill office buildings were evacuated Thursday as the Capitol Police investigated an "active bomb threat” related to a suspicious vehicle.

The FBI arrived on the scene Thursday morning in an effort to “engage in dialogue” with a man in the suspicious truck, according to Capitol officials with knowledge of the situation.

"Please continue to avoid the area around the Library of Congress," the Capitol Police said in a campus-wide alert.

Staffers in the Cannon and Jefferson buildings were told to use underground tunnels to move to other locations, and those in several other buildings were instructed to stay away from external doors and windows. Staffers in Madison, which houses the Library of Congress, were urged to evacuate.

Lawmakers are not in the building, with the House not scheduled to return for votes until next Monday. Hill staff and Library of Congress personnel were working on-site Thursday when the evacuations began, though it’s unclear how many staffers were in the building, with many offices allowing their staff to work from home.

For many Hill staffers, the emergency alerts renewed a sense of anxiety for those who had been in the building for the Jan. 6 riots, with some campus-wide security questions still unanswered. Several pipe bombs were found at the RNC and DNC on Jan. 6, but the perpetrator was never caught.

The call to evacuate the Cannon House Office Building went out just after 10:00 a.m as staff were told to "remain calm and relocate." Capitol Police first alerted staffers to the suspicious vehicle threat shortly after 9:30 a.m. EST.

Capitol Police relocated press to the opposite side of the Capitol while they investigated the threat. Officers waved drivers away from the avenues leading up Capitol Hill.

Earlier in the week, a suspicious package near the Library of Congress prompted a Capitol Police investigation Tuesday, but the road closures and investigation were ended in just under an hour.

Katherine Tully-McManus contributed to this report.

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