Fire officials say it happened around 6:30 p.m. on the 400 block of South Potomac Street. They say heavy flames were burning from the side of a vacant commercial building.
When fire crews got to the scene, the smoke was at ground level because of the high winds and it was so thick they couldn't even tell which building the flames were coming from.
Hagerstown Fire Marshal Douglas DeHaven says at this point there are no reports of injuries. He also says the fire was contained to the vacant building.
Officials say the building was once used as a garage for truck maintenance.
"Right now the building was vacant at the time we're still looking into that," says Fire Marshal DeHaven. "There's equipment left, but we don't think it was actively being used."
Potomac Street was closed between Lee Street and Memorial Blvd.
Fire Marshal DeHaven says they're still in the preliminary part of the investigation. We'll tell you exactly how this blaze started as the investigation unfolds.