ROANE COUNTY (WVLT) – The cause of a late Sunday afternoon industrial fire remains unknown.

Roane County dispatchers said it started just before 4:00 PM at the Horsehead Corp. plant in Rockwood.

Crews from every fire department in the county were called in to help extinguish the flames, which took nearly two hours.

The Horsehead Corp. Website says the plant was built in 1978 and purchased by the company in 1989. It is used to convert the electric arc furnace dust produced by steel mills into crude zinc oxide and iron-rich material.