The state Department for Environmental Protection on Thursday cited Hitachi Automotive Systems Americas in Berea for discharging contaminated wastewater last month.
Water samples showed levels of what's called hexavalent chromium that were above state and federal water quality guidelines, according to a news release. The state noted that public health and drinking water supplies are not at risk.
Hexavalent chromium is a chemical used in the plant's automotive manufacturing process. The contaminated storm water was taken by tanker trucks to off-site disposal locations. Samples of stream water taken since the spill have shown the levels are now within an acceptable range, the state said.
State officials said in the statement that Hitachi representatives are "cooperating fully."