Firefighters expected to battle a fire at the old Pevely Farms Dairy complex in St Louis, MO.

About eight demolition workers were inside the factory at when the fire began just after noon Sunday, said Capt. Bob Keuss.

At its height, about 60 firefighters battled the blaze. Keuss credits an experienced command staff for calling them out about 15 minutes before the first of two portions of the structure collapsed. Two firefighters suffered minor injuries from falling debris.

Pevely Dairy moved to St. Louis in 1917 and made ice cream and other dairy products. Developers planned to covert some of the 10-acre site, which owner Prairie Farms shuttered in October, into housing, with stores on the ground floor.

Keuss said investigators are questioning the demolition workers