MISSOULA, Mont. (AP) — A Montana reservoir that had a suspicious result in testing for invasive mussels in 2016 has been cleared and the state has lifted a requirement for mandatory decontamination stations at the reservoir east of Helena.

Mussels were detected east of the Continental Divide in Tiber Reservoir and in Canyon Ferry east of Helena, the Missoulian reported Monday.

Canyon Ferry was removed Friday from a list of bodies of water confirmed or suspected for aquatic invasive mussels after it recorded a suspicious result in 2016, the state Department of Fish, Wildlife and Parks said.

Aquatic mussels have no natural predators and can clog water pipes and displace native species.

The change means boaters will no longer have to complete a mandatory inspection when leaving Canyon Ferry.

Those rules are expected to remain in place at the Tiber Reservoir. The reservoir has had no positive tests in three years but restrictions, including a certified boater program and decontamination stations, will remain in place for at least two more years, department officials said.

Last year, Montana conducted about 99,000 watercraft inspections and intercepted 16 boats with invasive mussels coming into the state, officials said.