Tokyo Electric Power Company says an operation to transfer highly radioactive water pooled in the turbine building of the Fukushima Daiichi nuclear power plant's No.3 reactor caused contamination of the sea nearby.

Highly radioactive water was found leaking into the sea from a pit near the reactor's water intake on Wednesday.

The utility company says 1,200 becquerels of radioactive cesium 134 were detected in one cubic centimeter of sea water near the water intake on Thursday. The figure is 20,000 times the state limit. 1,200 becquerels of radioactive cesium 137, which is 13,000 times the state limit, were also detected.