US Capitol goes on lockdown after ‘external security threat’ and smoke seen behind the building

Rehearsals for the inauguration began Monday morning, but shortly after 10 a.m. EST smoke was seen on the east side of the U.S. Capitol building.

MSNBC's Garrett Haake said that over the Capitol loudspeaker it was announced that people inside must shelter in place and stay away from doors and windows due to an "external security threat."

Capitol Hill staffers were sent a message saying: "The West Front of the Capitol has just been evacuated. We've been moved, staff were sent this notice: All buildings within the Capitol Complex: External security threat, no entry or exit is permitted, stay away from exterior windows, doors. If outside, seek cover. USCP"

Interstate 295 is one of the only roads that can be used through the area surrounding the U.S. Capitol ahead of the inauguration and the smoke appeared to be coming from that direction. Reporters in the area noticed security locking gates and clearing people around the security checkpoints.

Officials told the Associated Press that the evacuation of the inaugural rehearsal was prompted by a fire several blocks away. It is "not believed to be a threat."

National Guard soldiers told one reporter that it was a propane tank that exploded.

Photos posted to social media showed what appeared to be a homeless encampment on fire.