LIVE: Capitol buildings evacuated as police respond to reports of explosive in truck -- negotiators sent to engage suspect

According to the Associated Press, authorities are responding to a reported bomb threat from a truck near the Library of Congress, with an evacuation for the area ordered in an instant security alert. Capitol staffers being told to shelter in their offices.

"The USCP is responding to a suspicious vehicle near the Library of Congress," stated the Capitol Police on its social media account. "Please stay away from this area and follow this account for the latest information."

According to a CNN report, police are "sending negotiators to engage" with the man in the suspicious truck.

Watch a live stream, courtesy of Fox 8 News, below: