The US Capitol building was placed under lockdown after smoke was seen nearby forcing those taking part in the inauguration rehearsal to leave.

Smoke above the Capitol building sparked a lockdown as tensions remain high in ahead of the Biden inauguration. 

Staffers were sent a message urging them to stay away from windows with a message sent at 16:20 UK time reading: “All buildings within the Capitol Complex: External security threat, no entry or exit is permitted, stay away from exterior windows, doors. If outside, seem cover. USCP”

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A nearby fire is now thought to be the cause of the smoke.

DC fire department confirmed that crews "responded to an outside fire in the 100 block of H St SE that has been extinguished. There were no injuries. This accounts for smoke that many have seen." 

The warning comes as the Capitol remains on high alert ahead of the event on Wednesday. 

The lockdown comes as US defence officials said they are worried about an insider attack or other threat from service members involved in securing President-elect Joe Biden's inauguration, prompting the FBI to vet all of the 25,000 National Guard troops coming into Washington for the event.