ANCHORAGE, Alaska (AP) -- Alaska polar bears are losing their fur and U.S. Geological Survey scientists don't know why.

In the past two weeks, nine of 33 bears checked by scientists in the southern Beaufort Sea region near Barrow were found to have alopecia _ loss of fur _ and skin lesions, said Tony DeGange, chief of the biology office at the USGS Science Center in Anchorage.

Three of four bears inspected Thursday near Kaktovik showed the symptoms as well.

Scientists have been collecting blood and tissue samples from the afflicted bears, but they do not know the cause or the significance of the outbreak, the Anchorage Daily News reported.

``Our data set suggests that this is unusual but not unprecedented,'' DeGange said. Ten of 48 bears checked by the team in 1998-99 had a similar condition, he said.

In a long-standing project, the USGS has sent polar bear research teams to the area since 1984. The teams track, sedate and examine the bears to help determine their general health and habits.

This year they saw their first bear with hair loss on March 21. The team will wind up this year's operations in May when the sea ice becomes too treacherous for safe travel.

``We took biopsies in `99 and couldn't establish a causative agent for the hair loss then,'' DeGange said. ``But now we have this unexplained mortality event going on with seals. And they haven't been successful in figuring out what caused the seal deaths. Is it just a matter of coincidence or is it related? We don't know.''

In December, the National Oceanic and Atmospheric Administration declared an ``unusual mortality event'' based on a number of ringed seals hauled out on beaches on the Arctic coast of Alaska during the summer. Dead and dying seals were found to have hair loss and skin sores.