Japanese whalers caught two animals along the northern coast that had traces of radiation, presumably from leaks at a damaged nuclear power plant, officials have said.
Two of 17 minke whales caught off the Pacific coast of Hokkaido showed traces of radioactive caesium, 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 caesium 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 before and after the Fukushima crisis.
The government has banned fishing around the coastal nuclear plant. Local government and fisheries officials have been monitoring radiation in seafood along the coast weekly.
The March 11 disaster knocked out power and crucial cooling systems at the Fukushima plant, melting fuel in three reactors and leaking massive radiation into the environment.
Some radioactive water was released from the plant into the ocean, causing concerns about contamination of seafood.
The leakage stopped after the plant operator sealed cracks, built oil fences around the plant and took other steps.