A Williston Fire Department official says a massive blaze at an oil supply and logistics company in the western North Dakota town has been extinguished.
Shift captain Steven Kerzmann says most firefighters returned from the scene late Tuesday, though one truck remained at Red River Supply to monitor hot spots.
Kerzmann says the department is not sure what caused the fire that first started around midnight Monday.
State records show several flammable chemicals were on the company's property. The company's website says it provides storage, blending and delivery of drilling fluids. The company did not respond to a request for comment.
Williston Fire Chief Jason Catrambone said Tuesday that officials couldn't identify which chemicals had burned.
The state Health Department was monitoring air quality.