Tokyo Electric Power Company (TEPCO), the operator of the crisis which hit Fukushima No. 1 nuclear power plant, admitted that more waste water contained strontium leaked into the sea early Thursday.

According to the TEPCO, about 12 tons of waste water with high levels of radioactive strontium leaked from a pipe connected to the waste water tank. The workers found the leaking and stopped it by shutting the valve.

TEPCO is still trying to find out how the pipes disconnected and the exact volume of the waste water. TEPCO said the waste water contains 16.7 becquerels of radioactive strontium per milliliter.

On March 26, radioactive waste water leaked from another part of the same facility. TEPCO said that they are planning to change the pipes to avoid the leaking accidents.