UPDATE: A man who claimed to have a bomb in a pickup truck near the U.S. Capitol has surrendered to law enforcement after an hourslong standoff that prompted a massive police response and the evacuations of government buildings and businesses in the area. Police say they did not find a bomb in the vehicle but possible bomb-making materials were collected from it. Authorities are trying to learn what led the man, identified by law enforcement officials as 49-year-old Floyd Ray Roseberry of North Carolina, to drive onto the sidewalk outside the Library of Congress and make bomb threats to officers.

EARLIER: Law enforcement authorities say a man sitting in a black pickup truck outside the Library of Congress has told police that he has a bomb. That’s led to a standoff in the heart of the nation’s capital. Law enforcement officials are trying to determine whether it’s a real bomb. Capitol Police Chief Thomas Manger says police have evacuated multiple buildings around the Capitol after officers observed the man holding what appeared to be a detonator. The man’s name was not immediately disclosed. Police negotiators are said to be communicating with him as he writes notes and shows them to authorities from inside the truck.