KALISPELL — A spokeswoman says Interior Secretary Ryan Zinke has canceled plans by Glacier National Park to ease restrictions on the use of motorized boats from outside the park.

Boating has been restricted at Glacier since invasive mussels were found last fall in a Montana reservoir about 100 miles away.

Interior spokeswoman Heather Swift said Tuesday that the park had mistakenly moved to ease restrictions for all boats after Zinke urged lifting them for the boats of private landowners within the park's boundaries.

After Swift spoke, Glacier issued a press release retracting its Monday announcement that restrictions would be eased on all boats in coming weeks.

The release said the original announcement had been premature.

Conservationists, among them former Glacier Superintendent Chas Cartwright, criticized the reversal as risky.

"They had a plan to minimize the risk, and the plan was to close all park waters to all motorized craft for this field season," Cartwright said when Zinke's original plan was announced. "... I am flabbergasted that we would consider opening park waters now."

Glacier closed park waters to all boating last November, when invasive mussel larvae were found in Tiber Reservoir on the Marias River southwest of Chester.

The tiny, striped shellfish multiply rapidly and can be spread to other bodies of water by latching onto boats, wading boots and other objects. Mussels can damage beaches, clog boat motors, harm fish and block irrigation equipment and water intakes.

As a result of the positive test, Montana added more boat inspection and contamination stations, and out-of-state watercraft will have to be inspected prior to launching in any Montana waterway.

With the inspection sites in place, some bodies of water that had been closed have re-opened.

In March, Glacier park opened its waters to non-motorized craft and later allowed rental or chartered motorized boats that had remained in the park.

The park said Monday it had begun allowing landowners around Lake McDonald to launch motorized boats and that it would soon announce an inspection and 30-day quarantine procedure that would allow other motorized boats in the park.

"Our objective is to provide an appropriate level of user access to the extent that we can, and ensure that those motorboats do not pose a risk to park waters," Superintendent Jeff Mow said Monday.

Swift called it "a common-sense measure that is consistent with Montana's values of recreation and multiple use of public lands."

David Brooks, executive director of Montana Trout Unlimited, called that initial decision irresponsible.

"It's an open door to the Columbia River Basin that shouldn't be opened unless Glacier is fully staffed and has the resources necessary to inspect and decontaminate every boat," Brooks said.