A radiation surge at Japan’s stricken Fukushima nuclear plant temporarily forced the remaining workers there to pull out.
White smoke could be seen billowing from the complex; it is thought a fuel pool at the No.3 reactor may have heated and produced what could be steam.
Fifty employees were eventually allowed to return after radiation levels fell again. However the government may now seek direct US military help to end the crisis.
The site has has been hit by four blasts at four of its reactors after Friday’s earthquake and tsunami damaged the plant’s cooling functions. Two other reactors are now said to be causing concern.
Fears of radiation leaks have prompted the government to establish a 30-kilometre exclusion zone. Some 70,000 people have been evacuated.
But many people outside the area are still worried about radiation exposure and are being tested.