A Tepco official said that workers had found that some water with a radioactivity of 1,000 millisievert per hour, had accumulated in a pit near reactor number two's water intake facility.
"They then found that a 20 centimetre crack had emerged in the pit and that radioactive water was leaking directly into the sea," he explained.
Tepco says it plans to fill the crack with cement while checking radiation levels in sea water at three locations 15 kilometres offshore. Earlier the company announced that radioactive iodine-131 in groundwater below the nuclear plant was 4,000 times higher than the safe levels set by the government.
Meanwhile Prime Minister Naoto Kan visited the area on Saturday where the devasting earthquake and tsunami struck on 11 March. In his first ground visit to the disaster zone, he toured evacuation centres and the community of Rikuzentakata where 1,049 people are confirmed dead and 1,253 are still missing.
Kan then headed to 'J village' in Fukushima, the base for hundreds of emergency crew who are working to prevent a wider disaster at the nuclear plant. Talking to workers he said they could not afford to lose the battle to stabilise the plant.