Officials were investigating Wednesday evening after several people reported smelling an unusual odor across towns in Madison County.
The village of East Alton said in a Facebook post that residents there and in several other towns northwest of Edwardsville reported the odor, including Roxana, Wood River, Hartford and Alton.
An Ameren Illinois spokesperson said it had investigated several calls and had not found any gas leaks in its system.
The smell could possibly be coming from the local refinery or landfill, East Alton said, but a cause had not yet been determined.