Japan's nuclear safety watchdog said Monday that a leakage of about 1.5 tons of low-level radioactive water occurred at a plant of Japan Atomic Power Co. in the village of Tokai in Ibaraki Prefecture.

The Nuclear and Industrial Safety Agency launched investigation to check whether the water had leaked into the sea.

The water was used to decontaminate radiation protection suits and other items and was contaminated to an extent of 33 becquerels per gram, Kyodo News said, adding the leakage occurred when water was transferred from a storage tank to another tank of a nuclear reactor during decommissioning Wednesday.