An incident at a chemical plant in downtown Elwood, Ill., led to a chemical spill that sickened 18 people on Nov. 5, reports said.

The local fire department, ambulances and a hazardous materials crew from Will County were sent to the Stepan Chemical Company facility on West Millsdale Road, about 10 miles south of the city of Joliet, in response to an alert over the release of a heat transfer fluid known by the brand name Therminol. Officers with the sheriff's department also arrived at the scene to assist with traffic control.

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According to Stepan Chemical Company spokeswoman Kim Kumiega, the incident occurred shortly after planned maintenance had been completed and while the system was being started up. Kumiega said that there had been "a small release" and that 18 workers had been exposed to vapors. However, 16 of them refused treatment and only two were transported to hospitals, a statement emailed to the Chicago Tribune said.

Meanwhile, Will County sheriff's spokeswoman Kathy Hoffmeyer confirmed that the chemical release occurred when workers were lifting a unit which "over pressurized." The direct cause of the incident is still not known. Hoffmeyer explained that there had not been an explosion at the plant at any time and there was no risk to public health or the environment.