Cesium-137 readings near the plant's Reactor 2 were 830 becquerels per litre, compared with the regulatory limit of 90 per litre. Both Cesium-134 and Cesium-137 are harmful to humans.

The latest water samples contain "high density of tritium and strontium," a TEPCO spokesperson said, adding that he had no new information on the condition of six Fukushima workers who were doused with radioactive water as a result of human error.