Workers have been evacuated from the stricken Fukushima nuclear plant in Japan after a plume of smoke rose from one of the reactors, the operator has said.
okyo Electric Power Company spokesman Hiroshi Aizawa said the firm was investigating after the light grey smoke was seen rising from the spent fuel storage pool of unit three.
Officials at the Dai-ichi plant have been battling to cool reactors and fuel pools to bring the radiation-leaking plant under control.
The facility was badly damaged in the massive earthquake and tsunami on March 11 that devastated northeast Japan.
Speaking after the smoke was seen, the spokesman said: "Due to this problem, the operator temporarily pulled out the workers, while checking on the condition of the site."
Earlier in the day, Japan's prime minister Naoto Kan said engineers were making "slow but steady progress" in dealing with the atomic crisis at the plant.
Experts have managed to restore power to two of the six reactors.
This represents the first breakthrough at the Fukushima plant since it was catastrophically damaged more than a week ago.
Tokyo Electric Power Company said units five and six were safe after days of pumping water into the reactors' pool brought temperatures down.
Meanwhile, over 500 Britons in Japan have been given iodine tablets to counteract radiation from the crippled nuclear facility - as the country's tsunami death toll rose to 18,000.
The Foreign Office said the tablets, which are used to stop the body absorbing radioactive iodine, have been distributed to around 540 British nationals so far.
The revelation came as police revealed the new death toll from the devastating 9.0-magnitude earthquake and tsunami.
A Foreign Office spokeswoman said the tablets were handed out only to those people who had requested them.
She added: "The British Embassy is distributing iodine tablets in Tokyo and Niigata as a contingency measure.
"People should wait until advised to take the tablets. Iodine tablets have been distributed to around 540 British nationals."