WEST GLACIER, Mont. (AP) -- A man and his daughter hiking in Glacier National Park suffered bite wounds and other injuries Thursday when they surprised a female grizzly and her cubs on a popular hiking trail, park officials said.

Names of the out-of-state hikers were not released.

Park spokeswoman Amy Vanderbilt said both had to be airlifted from a steep hillside, which they had rolled down in an effort to escape the bear.

They were reported in critical condition Thursday night at Kalispell Regional Medical Center.

"What we know at this point is that these hikers had a close-range encounter with a mother grizzly and her two cubs," she said. "The hikers reportedly sustained bites from the female grizzly and they may have other injuries. ... They rolled about 30 feet down the embankment."

Vanderbilt said the incident occurred at about 10 a.m. on the Grinnell Glacier Trail, about two miles above Josephine Lake. The trail is very popular with day hikers. Another hiker apparently found the victims, ran down the trail and reported it to a ranger who was leading a guided hike. Park officials temporarily closed the trail and surrounding areas to visitors.

Vanderbilt said park rangers were investigating, but typically no action is taken against the bears if it's determined the incident occurred because of a surprise encounter.

This was the first instance of a bear-related injury this year in the park, officials said.