Some 8.5 tons of radioactive water leaked from a reactor at Japan’s crippled Fukushima Daiichi nuclear power plant but it had not flowed outside the reactor building, Kyodo News said on Wednesday, quoting the plant’s operator.

Tokyo Electric Power Company said the leak occurred in the No 4 reactor after a pipe connected to the reactor dropped off, the news agency reported.

The leak was discovered Tuesday night and was stopped shortly afterwards.