MINNEAPOLIS (WCCO) – Zebra mussels have been confirmed in a large Twin Cities lake.

The Minnesota Department of Natural Resources says the invasive species were found this fall in Medicine Lake, which is in the suburbs just west of Minneapolis.

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“After at least six years of reports of zebra mussels on Medicine Lake that turned out to be negative, it’s disappointing to make this confirmation,” said DNR invasive species specialist Keegan Lund, in a news release.

Officials say a single zebra mussel was found on a dock that was being removed from the lake. Not long after, officials found two more adult zebra mussels on docks in other locations.

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The DNR says that fall is an important time for property owners to check for zebra mussels, as docks and boat lifts are being removed from lakes.

Recently, a single zebra mussel was found in Minneapolis’ Lake Harriet, and the entire Minnesota River was added to the infested waters list.

Minnesota law requires boaters and anglers to help in curbing the spread of invasive species.

Whether or not a lake is infested, boaters must keep watercraft clean of invasive species, drain all water before transport and dispose of unwanted bait in the trash.

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Zebra mussels are harmful to Minnesota lakes because they compete with native species for food and habitat, cause damage to water intake pipes and cut the feet of swimmers.