TOKYO — Highly radioactive water is leaking directly into the sea from a damaged pit near a crippled reactor at the Fukushima Daiichi Nuclear Power Station, Japanese safety officials said Saturday. The leak was the latest setback in the increasingly difficult bid to regain control of the plant.

Although higher than normal levels of radiation have been detected in the ocean water near the plant in recent days, this is the first time the source of any leaks was found.

Because the government did not report the levels of radioactive materials in the waters near the stricken plant on Saturday, it was difficult to judge how dangerous the levels of radiation were for fish or for humans who might come in contact with it. The government has already set up an evacuation zone for 19 miles around the plant, and fishing in the area has been suspended since the earthquake and tsunami.

Hidehiko Nishiyama, deputy director general of Japan’s nuclear regulator, the Nuclear and Industrial Safety Association, said it was possible that the leak was behind the elevated radiation levels near the shore found in recent days. The government announced Saturday that higher than normal levels of radioactive materials were detected about 25 miles south of the plant, much farther than had previously been reported.