BILLINGS, Mont. — A closed aluminum plant in Columbia Falls was designated by federal officials on Wednesday as an environmentally-contaminated Superfund site that needs to be cleaned up.

The Environmental Protection Agency announcement will allow further investigation of the Columbia Falls Aluminum Co. to determine its risk to human health, agency officials said.

The plant, located on 960 acres on the banks of the Flathead River near Glacier National Park, operated from 1955 to 2009. It’s owned by Glencore, a Swiss commodities firm.

The site became eligible for Superfund status after potentially hazardous materials were discovered in soil, groundwater and surface water at the plant site, and cyanide contamination was found in sediment in the Flathead River.

Under Superfund designation, the EPA can require polluting companies to cover the cost of cleaning up pollution. The former aluminum plant is the 17th site in Montana to make the list, joining former mining sites, the asbestos-contaminated town of Libby and others.

Glencore has owned the Columbia Falls plant since 1999 and had discussed re-opening it in recent years. The EPA began moving forward with a potential Superfund listing last year, just one day after plant managers said the closure was permanent.

The plant’s project manager, John Stroiazzo, said the company was disappointed by the Superfund listing but would continue to work on the site as required under an earlier agreement with the EPA.

He said addressing the site through a process other than Superfund designation would have increased the chances it could be redeveloped quickly and put back into beneficial use.

“Listing the site is not in the best interest of the project or the community,” Stroiazzo said.

U.S. Rep. Ryan Zinke warned the Superfund designation will drive down area property values and hinder economic development.

But U.S. Senator Jon Tester said the Superfund designation will make sure Glencore is held accountable for the cleanup after “years of broken promises and stonewalling.”

“Glencore can no longer try and turn their back on families in Columbia Falls,” Tester said in a statement.