ST. PAUL, Minn. (AP) — Three environmental groups have sued the state of Minnesota, accusing it of letting North America's largest taconite mining operation pollute lakes and streams for decades.

The tailings pit at the Minntac mine near Mountain Iron is owned by U.S. Steel. It operates under a state permit that expired 24 years ago. The permit has not been updated with standards to protect water, wildlife and wild rice.

The Star Tribune reports the lawsuit filed Wednesday alleges the pit's discharges violate water pollution laws and killed wild rice that once thrived nearby.

A Minnesota Pollution Control Agency spokesman says the agency can't comment.

The MPCA has held off on updating Minntac's permit until it creates a revised sulfate standard for protecting wild rice. It expects to finish that work in 2018.