A utility restarted a water treatment plant in northwest Indiana a week after idling it after iron-contaminated sewage was released from a US Steel plant in a tributary of Lake Michigan.

Indiana American Water said it restarted its Ogden Dunes treatment facility on Sunday after water sampling results confirmed the release did not impact its Lake Michigan water source .

The utility used water from a treatment facility in Gary to meet the needs of its customers during the precautionary shutdown that began on September 26 after the US Steel Midwest plant in Portage sent a plume of rust colored containing high levels of iron in the Burns Waterway.

The U.S. Environmental Protection Agency said last week that preliminary sampling results showed reddish-orange releases from the Portage steel plant, about 30 miles east of Chicago, did not presented no threat to public health.

The EPA and the Indiana Department of Environmental Management said they were continuing to investigate the cause of the release, as well as possible Clean Water Act compliance issues and environmental impacts.

US Steel shut down the Portage plant for several days after the rejection. The steel plant was put back into service on Wednesday.

The landfill also resulted in the closure of the Portage Riverwalk and the Lakefront and beaches in Indiana Dunes National Park. The park reopened its beaches on Wednesday.