The United States Capitol Police are investigating an “active bomb threat” near the U.S. Capitol, prompting the evacuation of the complex.

USCP Chief Tom Manger said authorities seized on a black pickup truck early Thursday that had been driven on the sidewalk outside the Library of Congress building by a man claiming to have an explosive device.

When approached by officers, the driver told officers that he had a detonator in his hand, Manger said.

The chief said department negotiators have been communicating with the driver in an effort to bring “a peaceful resolution to this incident.”

Manger did not name the driver, but the chief said investigators have confirmed his identity.

“We don’t know what his motives are,” Manger said.

MEDIA ALERT: This is an active bomb threat investigation. The staging area for journalists covering this situation is at Constitution and First Street, NW for your safety.

Please continue to avoid the area around the Library of Congress. pic.twitter.com/jTNVaBmVwR— U.S. Capitol Police (@CapitolPolice) August 19, 2021

Several congressional staffers confirmed to USA TODAY they have been told about the active bomb threat. According to alerts sent by the USCP, they have also closed down roads surrounding the Capitol complex and have evacuated most of the office buildings.

Capitol Police are leading the response that includes the FBI, Bureau of Alcohol Tobacco Firearms and Explosives and the D.C. Metropolitan Police.

In a brief statement, the FBI’s Washington Field Office referred to “reports of a suspicious vehicle and bomb threat near the Library of Congress.”

Both chambers of Congress are currently out of session for their summer breaks . Most lawmakers are currently not in their D.C. offices. 

Patricia McCabe, a public information officer for the Supreme Court, said the Supreme Court building was also evacuated shortly after 10 a.m. EST Thursday morning. It is closed to the public because of the coronavirus pandemic.

Washington, D.C. Mayor Muriel Bowser said she had been briefed on the continuing investigation and urged the public to stay away from the Capitol area.

I have been briefed on the evolving situation near the Library of Congress. The @DCPoliceDept is assisting the U.S. Capitol Police in the response, and will provide an update when there is additional information to share. For now, please avoid the area near the Capitol.— Mayor Muriel Bowser (@MayorBowser) August 19, 2021

The threat of an explosive near the Capitol recalled a chilling aspect of the Jan. 6 riot investigation that remains unresolved.

Two pipe bombs were placed near the headquarters of the Republican and Democratic national committees the night before the deadly Capitol siege. In that investigation, federal authorities have repeatedly appealed for the public’s help in locating a suspect seen wearing a gray hooded sweatshirt.

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This article originally appeared on USA TODAY: US Capitol Police investigating ‘active bomb threat’ on Capitol Hill; complex evacuated