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 reported that the EPA issued a violation notice to KCBX Terminals Co. on Tuesday.
The EPA said 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.
A spokesman for KCBX parent company, Koch Industries, said the monitors didn't measure pollution in the neighborhoods, and the company is reviewing how the EPA determined there was a violation.