Firefighters in San Francisco this morning are investigating a possible fire at the department’s downtown headquarters, a fire dispatcher said.

Units first responded to reports of smoke emitting from a vent in front of the building of San Francisco Fire Department headquarters at 698 Second St. at around 11:15 p.m. Thursday, the dispatcher said.

Smoke was also spotted coming from an air-conditioning vent on the building’s roof, though the potential blaze was quickly extinguished, the dispatcher said.

The exact source of the smoke has not yet been determined, and fire officials are investigating.

There were no reported injuries.

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