It started around 5:45 a.m. at the Johns Manville facility on the 400 block of North Grove Street.
The view from Chopper 6 showed smoke billowing from the building, but no flames could be seen.
Officials said all occupants were accounted for and no injuries have been reported.
The cause of the fire has not been determined.
The Johns Manville company manufactures insulation and roofing materials.