About 100 tonnes of water containing high levels of radioactive material leaked at the damaged Japanese nuclear power plant in Fukushima, the operator of the plant said on Thursday.
Tokyo Electric Power Co said it had detected the leak from a storage tank at the Fukushima Daiichi Nuclear Power Station Wednesday night.
The leak was the largest since about 300 tonnes of highly-contaminated water escaped from another storage tank in August.
The operator said the latest leak had stopped earlier on Thursday and that they did not believe the contaminated water had reached the Pacific Ocean.
The plant suffered meltdowns at three of its six reactors after a tsunami swept through the complex nearly three years ago.
Tokyo Electric is injecting water into the reactors to keep them cool, and has been battling with leaks from storage containers where the resulting radioactive water is being stored.