Hamilton firefighters were called to National Steelcar for an early morning blaze.
Fire officials believe a spark ignited combustible materials in the company’s dust collection system.
The building’s sprinkler had the blaze under control when firefighters arrived, but crews had to open the dust collection system and remove the filter to put out the fire.
The flames didn’t spread to the rest of the building, and all employees managed to escape without injury.
Damage is estimated at $750,000.