Japanese officials said on Friday that workers trying to cool quake hit nuclear reactors were exposed to radiation levels 10,000 times higher than expected.
Engineers have been working to repair the six-reactor Fukushima nuclear plant since the massive tremor and tsunami struck two weeks ago.
READ – Japan Disaster Data links
Authorities said three workers had been taken to hospital after suffering burns and have vowed to step up safety measures.
Police say more than 10,000 people have died since the twin natural disasters.
More than 17,400 people are missing, and some 2,700 have been injured.
Meanwhile, the disaster has badly hit Japan’s tourist industry.
There are reports of mass cancellations by travel companies with holidaymakers worried about being exposed to radiation.