Indiana Dunes National Park beaches closed after steel factory dumps 'rusty liquid' into waterway

Beaches at Indiana Dunes National Park were closed on Monday because a mystery liquid was dumped into a waterway that leads into Lake Michigan.

The National Park Service said that on Sunday evening, someone reported a "discharge of rusty colored liquid" into the Burns Waterway, which is alongside the U.S. Steel Plant. Indiana Dunes National Park sits just west of there, along Lake Michigan.

The National Park Service said an investigation is underway to determine "the nature and extent of the discharge."

Portage Mayor Sue Lynch told FOX 32 Chicago that the city had closed Lakefront Park while awaiting test results from EPA, IDEM and US Steel.

As a precautionary measure, Indiana American Water said it shut down its Ogden Dunes water treatment facility in northwest Indiana Sunday evening. "Indiana American Water performs continuous real-time monitoring at our Ogden Dunes treatment facility, and although we have seen no impact on the raw water parameters we are monitoring for at this location, the treatment plant will remain offline until such time as additional data and water testing results confirm there is no threat," the company said in a statement.