TOKYO - Japanese whalers have found traces of radiation in two animals caught along the country's northern coast, presumably because of leaks from a damaged nuclear power plant, officials said Wednesday.

Two of 17 minke whales caught off the Pacific coast of Hokkaido showed traces of radioactive cesium, both about one-twentieth of the legal limit, fisheries officials said.

They are the first whales thought to have been affected by radiation leaked from the Fukushima Dai-ichi nuclear plant since it was hit by a March 11 earthquake and tsunami.

"The levels are far below the limit, and the meat from the catch is safe for consumption," Fisheries Agency official Kosei Takekoshi said.

One of the minkes had a cesium reading of 31 becquerels per kilogram, and the other 24.3 becquerels, compared to the legal limit of 500 becquerels per kilogram for highly migratory marine products.

The 17 whales were caught off the shores of Kushiro city -- a main coastal whaling hub -- during an April 25-June 10 expedition.

The agency has not previously surveyed radiation in whales, so no comparison is available for exposure levels before and after the Fukushima crisis.

The government has banned fishing around the nuclear plant. Local government and fisheries officials have been conducting weekly radiation monitoring of seafood along the coast.

The March 11 disaster knocked out power and crucial cooling systems at the Fukushima plant, resulting in the melting of fuel in three reactors and massive radiation leaks into the environment.

Some radioactive water was released from the plant into the ocean, causing concerns about contamination of seafood.

Japan says the country's research whaling is for scientific purposes and is allowed by the International Whaling Commission as an exception to a 1986 ban on commercial hunts.

But opponents say it is a cover for commercial whaling because the whale meat not used for research is sold for consumption in Japan.