Tokyo battled to avert a meltdown at three stricken reactors at the Fukushima plant in the worst nuclear accident since the 1986 Chernobyl disaster, triggered by Friday's tsunami. Radiation levels were also up at the Onagawa atomic plant.
"This is not a serious public health issue at the moment," Malcolm Crick, Secretary of the U.N. Scientific Committee on the Effects of Atomic Radiation, told Reuters.
"It won't be anything like Chernobyl. There the reactor was operating at full power when it exploded and it had no containment," he said. As a precaution, around 140,000 people have been evacuated from the area around Fukushima.
The World Health Organization (WHO) also said the public health risk from Japan's atomic plants remained "quite low." The quake and devastating tsunami may have killed 10,000 people.
The Japan Meteorological Agency said that the winds in the area would shift from the south to a westerly on Sunday night, blowing from Fukushima toward the Pacific Ocean.