MARINETTE, WI — University of Wisconsin researchers say they’ve linked a plume of toxic PFAS chemicals entering Lake Michigan to a firefighting foam manufacturer.

In a new study, researchers used chemical fingerprinting to link contaminants entering Green Bay to Tyco Fire Products, a manufacturer along the Menominee River in Marinette, Wis., which is owned by Johnson Controls Inc.

The contaminants were tracked through groundwater, surface water and biosolid sludges. Tyco’s facilities in Marinette and Peshtigo have previously been identified as PFAS sources in groundwater and local private drinking water wells.