A report by the Indiana Department of Environmental Management this week says U.S. Steel violated its permit when it released excess iron into a Lake Michigan waterway last month, causing it to turn a rusty color.

U.S. Steel Midwest idled the plant in Portage, about 30 miles east of Chicago, as a precaution after it said a wastewater treatment facility experienced “an upset condition” that sent the rusty colored plume containing elevated levels of lead into the Burns Waterway on Sunday.

State and federal environmental agencies are working with U.S. Steel to investigate the cause of the leak and find out if it's harmful.

A federal judge has approved a revised settlement with U.S. Steel, more than four years after one of the steelmaker's Indiana plants discharged wastewater containing a potentially carcinogenic chemical into a Lake Michigan tributary.

A parks advocacy group says U.S. Steel's revised consent decree doesn't ensure protections for Indiana Dunes National Park.

The company reported the release to the Indiana Department of Environmental Management on Wednesday night.

U.S. Steel has reopened most of the Midwest Plant as of Tuesday, Nov. 5.

This spill comes just weeks after another leak from U.S. Steel and a chemical spill from ArcelorMittal that killed 3,000 fish.

U.S. Steel announced Friday the company will idle its East Chicago Tin mill where an estimated 150 workers could face layoffs.

U.S. Steel is planning to idle its East Chicago Tin plant, which makes tin-plated metal for uses such as food and paint cans, and lay off about 150 workers.