The Minnesota Department of Natural Resources has confirmed finding zebra mussels in two lakes in Itasca county.
DNR spokeswoman Cheri Zeppelin said a man who lives on Sand Lake was installing a dock last week when he found dried, dead adult zebra mussels attached to it. She said the mussels probably were there last fall.
Zeppelin said the DNR has started a search of adjoining bodies of water. It also has found mussels in Little Sand Lake.
Sand Lake, Little Sand Lake and other small lakes are part of the Bowstring chain of lakes that flow into the Big Fork River.
Zeppelin said that means the infestation could eventually spread.
"It takes a while for zebra mussels to establish through moving currents, but that potential is there. The key is to slow down the spread," Zeppelin said.
DNR aquatic invasive species specialist Rich Rezanka is evaluating the extent of the infestation.
"He's walking on the shore, looking for structures where zebra mussels would usually form," Zeppelin explained. "He's also using underwater cameras, but we're talking about several lakes in this group so it could take several days."
The Big Fork River flows north through Koochiching county up to the Canadian border.
Zeppelin says people using Sand Lake and Little Sand Lake now must remove vegetation all from their boats, drain the boats of water and possibly take them to a decontamination unit for a hot water, high-pressure spray cleaning.