BILLINGS, Mont. (AP) A rare attack by a river otter in southern Montana injured three women floating on inner tubes and inflicted wounds serious enough that one victim had to be airlifted to a hospital, authorities said Thursday.

The attack happened near the town of Cardwell on a remote stretch of the Jefferson River, a tributary of the Missouri River thats popular with anglers and recreational floaters.

At least one otter swam up to the adult women at about 8:15 p.m. Wednesday and attacked them, said Morgan Jacobsen with Montana Fish Wildlife and Parks. The women were able to get to shore, where one of them called 911, he said.

One womans wounds, on her face and arms, were so severe that the helicopter was used to fly her out, Jefferson County Undersheriff James Everett said. Her condition Thursday was unknown. The others had injuries to their arms.

Its just not something you run into very often, Everett said. Bears do it, moose too and ocasionaly a deer, but otters? Thats not normal.

Jacobsen said one of the women saw two otters beforehand but it was unclear how many were involved in the attack.