Pittsburgh-based U.S. Steel Corp. (NYSE: X) has restored operations at the Midwest Plant in Portage after a higher-than-allowed hexavalent chromium discharge last week, according to our partners at The Times of Northwest Indiana.

The steel mill near the Lake Michigan shoreline in Porter County shut down three systems last Wednesday after the plant exceeded its permitted limit of the compound into the Burns Waterway.

U.S. Steel spokeswoman Amanda Malkowski said the steel mill was now fully operational except for the tin line. The tin line remains down for reasons that are unrelated to the discharge, she told the paper.

"We're fairly pleased with the swiftness of how this has been handled," said Malkowski.

U.S. Steel would not comment on test results from the public bodies of water until it shares the outcomes with the Indiana Department of Environmental Management, according to the publication.

Hexavalent chromium is a carcinogenic chemical used in steelmaking. It was made famous by the movie Erin Brockovich.

Indiana American Water shut down its Ogden Dunes treatment plant after the chemical discharge and said it would remain offline until water testing results showed no threat to the source water, reported the paper.