The worst nuclear accident since Chernobyl is unfolding in Japan.
Large amounts of radiation have been released into the atmosphere overnight after a fire at another reactor at the Fukushima Daiichi plant.
Japanese prime minister Naoto Kan has said as radiation levels rise everyone within 20km of the plant needed to leave the area.
He said radiation has spread from these reactors and there is still a very high risk of further radioactive material being released.
Noriyuki Shikata, spokesperson for the Japanese prime minister's office, said that the government did not believe there would be "tangible or visible damage" to human health outside the 20km evacuation zone.
"There are three blasts, and two of them relate to the hydrogen being accumulated at the top of the structure," he told Today presenter James Naughtie.
"In spite of those explosions the core reactor has not been damaged."
But opposition politician Taro Kono, a member of Japan's Liberal Democrat party, said that the way the government had handled the press was "giving unnecessary fear" to the population.
Despite the fears, David Warren, UK ambassador to Japan, was confident that the advice issued by Japanese government was correct.
There was "no-need for the people outside of the exclusion zone to evacuate," he said.
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