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ROCKTON, Ill. — Emergency crews remain on the scene of a massive fire at a chemical plant in Rockton, Illinois.

The fire started around 7 a.m. Monday at Chemtool Incorporated, located at 1165 Prairie Hill Road.  The company manufactures fluids, lubricants and grease products which are distributed worldwide.

According to WTVO, approximately 70 employees were evacuated and were uninjured. Rockton Fire Chief Kirk Wilson said one firefighter was treated for injuries.

Following reports that the plumes of smoke were so big they were being picked up on weather radar, the Rockton Police Department at 8:46 a.m., posted an alert, warning that fire officials had ordered a mandatory evacuation near the plant. It told people to evacuate homes and businesses, and to await further instructions.

Wilson said that “at this point and time there is no danger to air quality at ground level,” but that given the enormous plumes of smoke, officials ordered the evacuation as a precautionary measure.

“We don’t want an environmental nightmare to occur,” he said.

Trisha Diduch, the planning and development administrator for Rockton, said she estimates about 1,000 people are affected by the evacuation order and the downtown area, which is just about a mile from the plant, is being evacuated. The order is for a 1-mile (1.6-kilometer) radius, she said.

Rockton Middle School, at 6121 Elevator Rd, has been set up as an evacuation site.

The fire chief also said that it will likely take several days for the oil-based fire to burn off.

Chemtool released a statement that said:

We have confirmed all on site are safe and accounted for. Our concern right now is for the safety of all our employees and the surrounding community. As a precaution, authorities have evacuated residents in a one-mile radius of the site.

We do not yet know what caused this incident, but we will be working with local authorities and with our own risk management team to determine what happened and identify any corrective actions. We will share more details as they are known.

Illinois Gov. JB Pritzker said his office was monitoring the situation in Rockton, adding, “My thoughts are with the first responders fighting this blaze and all impacted. If you’re in the area, please follow the instructions of local law enforcement to stay safe.”

A massive dark plume of smoke extended south-southeast from the fire, raining ash and debris on residents as far south as DeKalb.

U.S. Environmental Protection Agency investigators from Chicago were headed to the scene and would issue a statement later Monday, spokeswoman Rachel Bassler said. They were coordinating with the Illinois EPA, which also was sending a team, according to spokeswoman Kim Biggs.

Rockton is located in Winnebago County, near the Wisconsin border, about 95 miles 153 kilometers) northwest of Chicago.

This is a developing story. Check back for details.