The U.S. Environmental Protection Agency says a petroleum coke storage facility on Chicago's southeast Side violated the Clean Air Act.
The Times of Northwest Indiana reports that the EPA issued a violation notice to KCBX Terminals Co. on Tuesday.
It says monitoring data from Feb. 18 through May 10 show there was too much soot in the air, and dust samples from nearby homes found vanadium and nickel.
Petroleum coke, known as petcoke, is a grainy byproduct of oil refining often used as fuel in industry. It's been piling up along the Calumet River as refineries increase production.
Chicago and state officials have been working on rules to control potential petcoke pollution.
A spokesman for KCBX parent company, Koch Industries, did not immediately return a call Wednesday seeking comment.