A rehearsal for President-elect Joe Biden’s inauguration was disrupted Monday — and the US Capitol was temporarily locked down — when smoke from a fire at a nearby homeless encampment raised tensions simmering since the Jan. 6 riot by supporters of outgoing President Trump.

Security officials yelled, “This is not a drill!,” while directing people to a secure location inside the building, participants in the rehearsal told The Associated Press.

Staffers inside were also ordered to “stay away from exterior windows,” according to local ABC News affiliate WJLA and multiple other sources.  

Photos show people scrambling for safety amid folding chairs set up outside the Capitol and military officers in camouflage clothing — one carrying a trombone — rushing through a hallway amid the chaos.

Biden wasn’t taking part in the rehearsal.

The smoke came from a fire in a homeless encampment about a mile away that was unrelated to the inauguration preparations, officials said.

The blaze was extinguished by District of Columbia firefighters and the evacuation and lockdown were ordered as a precaution, officials said.

The scare came in the wake of the deadly Jan. 6 riot at the Capitol, which has left stretches of the Beltway heavily fortified and tens of thousands of National Guard troops deployed.