Highly radioactive water was found leaking into the sea from the damaged Fukushima Daiichi nuclear plant on Wednesday. It's now been revealed that contaminated water levels in the No. 3 reactor's turbine building were already alarmingly high by Sunday.

Tokyo Electric Power Company plugged the leak with concrete after it found highly radioactive water flowing into the sea through a pit.

Radioactive cesium 620,000 times higher than the government-set safety limit was detected from the leaked water.

The contaminated water was streaming from the outlet of a pipe for electric cables.