Excerpts from nbc5chicago.com:

Two Aurora firefighters suffered injuries after responding to a hazardous materials incident on Thursday morning when they were called to a building in the 600 block of West Illinois for an odor investigation. Employees reported that two chemicals had been accidentally mixed at the location, which created a vapor cloud that filled the room.

One employee that was in the room at the time was able to escape safely and 50 other workers evacuated the facility without incident.

Two firefighters, both of whom were wearing PPE and SCBA entered the area and immediately felt a burning sensation around their mask seals. They backed out of the facility, and were taken to a local hospital for observation and treatment for minor injuries.

The call was upgraded to a Level III hazardous materials incident When hazmat technicians entered the building, they found that the incident had been contained and that the chemical reaction had stopped. The building was ventilated and turned back over to management, who said they would keep the facility closed while an investigation into the incident was initiated.

There was no threat to the public during the incident, and no one else was injured.