Nine people were taken to hospitals Saturday morning after breathing in formaldehyde gas at an Elgin factory.
Three others were examined at the scene and refused medical treatment.
Elgin Fire Capt. Robb Cagann said they were called to Capsonic, 460 S. Second St., at 10:07 a.m.
A plastics injection molding machine had become too hot, and the pellets fed into it burned instead of melting, Cagann said.
Workers complained of burning eyes and difficulty breathing, he said. Some also said they were nauseated.
They were taken to Sherman and Presence St. Joseph hospital in Elgin and St. Alexius Medical Center in Hoffman Estates.
The South Elgin Fire Department's hazardous-materials team responded as well, checking the air quality inside the building. Capsonic maintenance workers were allowed in to clean the machine, and the company got the OK to resume work at 12:16 p.m.
Capsonic makes parts primarily for automotive use.