St. Clair County Crews Battle Reactive Chemical Fire

ST. CLAIR COUNTY, Ill. — Officials issued a shelter-in-place order Wednesday morning, Aug. 12, 2026, after a fire involving hazardous material broke out in the area of Sauget, Cahokia Heights and East St. Louis, according to the St. Clair County Emergency Management Agency.

The agency said the fire occurred south of Missouri Avenue between South 50th and South 19th streets. An Everbridge notification was sent to phones in the affected area.

Residents and people in businesses within the outlined area were advised to remain inside, close windows and avoid using systems that bring outside air into buildings.

In a 5:40 a.m. Wednesday update, St. Clair County Emergency Management officials identified the hazardous material as trichloroisocyanuric acid. The agency said crews were working on plume control using water, while also working to secure runoff because the product is reactive to water.

The shelter-in-place order remained in effect at the time of the update. Officials said the product is an irritant to the eyes, skin, and respiratory tract, and exposure should be avoided if possible.

Area fire departments were in place battling the fire, and that included Madison County, St. Clair County, and some of Monroe County.

East St. Louis School District has cancelled school classes for today because of the fire.

The agency said additional information would be released as it becomes available.