About 12 tonnes of radioactive water has leaked at the Fukushima Daiichi nuclear power plant in Japan, with the operator saying most of it may have flowed into the Pacific Ocean.
Tokyo Electric Power Company said the leak was found early on Thursday from a pipe attached to a temporary decontamination system. The water had already gone through part of the cleansing process.
The water contains significant amounts of radioactive substances after it is used to cool the reactors.
It is then put into the water-processing facility so it can be recycled for use as coolant.
TEPCO said the leak has been plugged.
The government claimed in December that the reactors were now under control.
In another incident last month, TEPCO said about 120 tonnes of radioactive water leaked at the plant's water decontamination system and about 80 litres seeped into the ocean.
The plant was crippled by explosions caused by the tsunami after the earthquake on 11 March last year.