(CNN) -- Residents were ordered to evacuate their homes after a chemical fire broke out Monday morning at the Chemtool Inc. plant in Rockton, Illinois.
The city fire department ordered a mandatory evacuation for all residents and businesses in a one-mile radius of the plant, police said in a message on Twitter.
Rockton Fire Chief Kirk Wilson said the city hopes to avoid "an environmental nightmare" that could occur if any of Chemtool's oil-based lubricants ran off into the nearby Rock River, about 300 meters (330 yards) west.
Speaking at a news conference, Wilson said the department's water-based firefighting suppression has stopped inside the building, and they're now letting the product "burn off."
One of their main concerns is product spilling into the Rock River, he said
Another concern is the large plume of smoke moving south and southeast from the explosion site. Wilson said that the city's hazmat team has performed air quality analysis and determined there's no compromise of air quality at ground level at this time.
Evacuations remain in place for a one-mile radius from the explosion site as a "precautionary measure," he said. About 150 homes are in the evacuation zone.
The burn-off at the plant is expected to take several days. Between 40-45 agencies and 150-175 fire personnel are currently on the scene. The cause of the "catastrophic incident" has not been determined, Wilson said
CNN affiliate WREX reported that city Wilson said the 70 employees at the factory were able to get out safely. When fire crews arrived, the flames were through the roof and clouds of smoke filled the sky.
CNN affiliate WIFR said one firefighter was injured. No other details were immediately available.
Explosion sounded like "a decent-sized firework"
Residents of Rockton, located about 15 miles north of Rockford near the state line with Wisconsin, reported hearing a series of explosions.
"My family and I live in the evacuation zone," Thomas Rollette told CNN. "We heard the explosions this morning and decided to check outside maybe five minutes afterwards when our dogs wouldn't calm down. By that point the smoke was already filling the sky."
He said the first explosion sounded "like somebody lit off a decent-sized firework."
"It wasn't until more and louder explosions came that I even thought something was going on. Seeing the wall of smoke outside just confirmed it for me, and pretty soon after they were telling the nearby residents to evacuate."
Company thanks first responders
According to the company's website, "Chemtool Incorporated offers a wide variety of lubricating greases to meet your needs."
The Lubrizol Corporation, which owns the facility, released a statement saying all employees were safe and accounted for.
"At approximately 7 a.m. today, local emergency personnel responded to a fire at the Lubrizol Corporation's Chemtool Facility in Rockton, Ill. 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," the statement said.
"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. We are grateful to our employees, first responders and safety forces responding to this incident."
Salvation Army staff and volunteers set up a mobile unit to provide food to first responders, the Salvation Army of Winnebago County said, according to WIFR.
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