London, Apr 11 (IANS): Polar bears in Alaska have been seen with missing patches of fur, and reports say it may be due to a "mystery illness" related to the nuclear accident at the Fukushima power plant in Japan.

Nine out of 33 bears studied were found to have alopecia -- loss of fur -- and skin lesions, Sky News reported.

"There's a lot we don't know yet, whether we're dealing with something that's different or something that's the same," said Tony DeGange, chief biologist for the US Geological Survey (USGS) Science Centre in Alaska.

A similar illness has killed around 60 ringed seals in the region.

Unlike the seals, the polar bears otherwise seem healthy and there have been no deaths, he said.

Ten of 48 bears checked in 1999 had a similar condition.

"We took biopsies in 1999 and couldn't establish a causative agent for the hair loss then. 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," he said.

The USGS has been sending polar bear research teams to the area since 1984. They track, sedate and examine the bears to help determine their health and habits.

The theory of the Fukushima effect, however, has not been proved, the report said.