TOKYO (AFP) - Japanese whale hunters have found traces of radioactive caesium in two of the ocean giants recently harpooned off its shores in the Pacific Ocean, a fisheries agency official said Wednesday. Two minke whales culled off the northern island of Hokkaido showed readings of 31 becquerels and 24.3 becquerels of caesium per kilogram, he said, adding that the cause may be the accident at the Fukushima nuclear plant. The level is far below the country's recently-set maximum safe limit for seafood of 500 becquerels per kilogram, he said. "There is no data available to compare whether the readings for radioactive materials are higher than normal," he said. "We will continue to monitor the development, as we do for all seafood and marine life" that is caught off the Pacific coast, he said. The Fukushima Daiichi nuclear plant has leaked radioactive water into the Pacific since it was battered by the March 11 earthquake and tsunami, which disabled cooling systems, triggering reactor meltdowns and explosions. The Japanese public and some marine life experts have voiced fears that radioactive material in the sea can concentrate among large and long-lived marine creatures at the top of the food chain. The government has banned fishing in areas near the crippled nuclear plant, and local governments and fishing cooperatives are conducting regular radiation screenings of seafood along the Pacific coast. Japan hunts whales under a loophole to an international moratorium that allows killing the sea mammals for "scientific research". Japan also argues that whaling is an integral part of the island-nation's culture, and whale meat is sold openly in shops and restaurants.