MADISON, Wis. (AP) — Wisconsin environmental officials said Monday that they’re monitoring cleanup of what they’re calling an accidental release of contaminated river and groundwater at a Marinette plant that manufactures fire extinguishers and fire suppression systems.

Department of Natural Resources officials said in a statement that they were notified of the release late Sunday evening. Representatives at the JCI/Tyco facility reported a mixture of river water and contaminated groundwater entered storm sewer drains which flow back to the Menominee River.

Past sampling has shown groundwater at the site is contaminated with arsenic and PFAS from prior discharges. PFAS are man-made chemicals that research suggests can decrease female fertility, increase the risk of high blood pressure in pregnant women and lower birth weights. The chemicals have been used for decades in a range of products, including firefighting foam, nonstick cookware and stain-resistant sprays.

The DNR in April ordered JCI/Tyco to provide clean drinking water for three homeowners after test results showed elevated PFAS levels in their wells.