Ten polar bears, an unusually large number, were seen swimming in open water off the northern coast of Alaska recently, some heading for shore and some heading toward the retreating ice in the Chukchi Sea, two federal officials confirmed Friday.

Susanne Miller, the biologist in charge of the polar bear project for the federal Fish and Wildlife Service, said 8 of the 10 bears spotted in the aerial survey had been within 15 miles of shore. One was 35 miles from shore and another one 50, but neither was more than 20 miles from the nearest arctic ice.

Bear sightings in open water were infrequent until about 2004, Ms. Miller said, but rising temperatures have melted much of the ice platform on which they live and hunt for seals.

In May, Interior Secretary Dirk Kempthorne put the United States polar bear population under the protections of the Endangered Species Act, primarily because of the loss of its habitat.