Dozens of homes in northern Illinois were evacuated Monday after A massive fire destroyed a chemical plant in northern Illinois on Monday forcing dozens of evacuations and producing smoke so thick that it could be seen for miles. Fire officials in Rockton, Ill., issued a mandatory evacuation order affecting about 150 homes near a Lubrizol Corp., facility in the town of about 7,600 along the Wisconsin border 100 miles northwest of Chicago.

The evacuation was ordered moments after first responders arrived at the scene at 7 a.m. to find the Chemtool facility completely consumed by flames as a thick, black plume of smoke spread hundreds of feet overhead. About 70 plant employees were safely evacuated from the facility while one firefighter sustained minor injuries. According to Rockton Fire Chief Kirk Wilson:  “The fire was through the roof when we arrived, and the cause remains unknown at this point. Everything is still under investigation.” There was no danger to people at ground level from contaminants, the chief added.

Emergency officials are opting to let the fire burn out rather than douse it with water because of possible contamination from the runoff reaching the nearby Rock River.