Officials say Japanese whalers have found traces of radiation in two animals caught this year off the country's northern coast, presumably the result of damage at a nuclear power plant.

Fisheries officials said on June 15 that two of 17 minke whales caught off the coast of Hokkaido showed traces of radioactive cesium, both about one-twentieth of the legal limit.

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

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

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