U.S. Steel Midwest Plant on the shore of Lake Michigan, with the Indiana Dunes Portage Lakefront and Riverwalk Trail in the foreground, in 2019. (Patty Wetli / WTTW News)

U.S. Steel is reporting that a“rusty colored” discharge that poured into Lake Michigan on Sundayfrom its plant in Portage, Indiana, was due to elevated iron levels.

“Analysis of the water from the outfall taken during the time of the incident showed elevated concentrations of iron causing the discoloration,” U.S. Steel spokeswoman Amanda Malikowski wrote in a statement emailed to WTTW News. “There are no indications of permit level exceedances for hexavalent and total chromium, as those sampling results came in well below permit limits.”

Rather than comment on or confirm the U.S. Steel assessment, the Indiana Department of Environmental Management, which is leading the investigation into the spill, said itis still awaiting sample results taken by U.S. EPA.

“Once the results are received and analyzed, we’ll provide an update,” said department spokeswoman Sarah Bonick.

U.S. Steel shut down the facility, known as Midwest Plant, as officials investigated the cause of the spill. The discharge flowed into the Burns Waterway, a ditch that runs next to the company’s steel mill and drains into Lake Michigan.

Sunday’s spill prompted the National Park Service to temporarily close the waters off all beaches at Indiana Dunes National Park, and Indiana American Water to shut down its treatment plant at Ogden Dunes, which draws water for northwest Indiana from Lake Michigan near the steel plant.

Portage Mayor Sue Lynch told the Times of Northwest Indianathat no attempt was made to contain the spill because it was discovered well after the fact, and the discharge had already entered Lake Michigan.

This latest incident comes just weeks aftercourts approved a consent decreerequiring U.S. Steel to pay penalties and reimburse costs related to a 2017 spill in which thecompany released hundreds of pounds ofhexavalent chromium, nearly 600 times the maximum permitted, into the Burns Waterway.

Hexavalent chromium is a toxic heavy metal used in a number of industrial processes. The chemical was made famous by the film “Erin Brockovich” and can cause cancer in humans when they are exposed to it by breathing, according to the EPA.

Contact Patty Wetli:@pattywetli| (773) 509-5623 |[email protected]