KITAKAMI (AFP) - Smoke belched from a stricken nuclear plant in Japan on Monday, disrupting urgent efforts to repair the cooling systems as Tokyo halted some food shipments owing to radiation worries. Rain meanwhile complicated rescue efforts and compounded the misery of tsunami survivors fearful of dangerous radioactive leaks from the wrecked Fukushima power station, which has suffered a series of explosions and fires. Japan has ordered the suspension of shipments of milk and certain vegetables including spinach from regions around the plant after abnormal radiation levels were found in the products, said chief government spokesman Yukio Edano. But "even if you eat and drink them several times it will not be a health hazard. So I would like you to act calmly," Edano said at a televised news conference. Workers were forced to evacuate from part of the troubled Fukushima plant, located 250 kilometres northeast of the capital Tokyo, after grey smoke rose from reactor number three, operator Tokyo Electric Power Co. said. The cause was unclear but it was not believed to be linked to the all-important efforts to restore power to the reactor unit systems, officials said. The smoke abated more than two hours later but white smoke was later seen rising from the number two reactor, although there were no immediate reports of an increase in radiation from the plant. Shortly before the crews' evacuation, Prime Minister Naoto Kan said there was "slow but steady progress" in dealing with the atomic crisis. Before the smoke incident, the nuclear safety agency had said engineers were close to restoring some functions in the control room of reactor number two, such as temperature and pressure instruments and the air filtering system. "As a result, the environment for workers will significantly improve," an agency official said. The cooling systems - designed to protect the plant's six reactors from a potentially disastrous meltdown - were knocked out by the 9.0-magnitude earthquake and tsunami that struck Japan's northeast Pacific coast on March 11. Fire trucks have been spraying water to help cool the reactor units, but those operations were also disrupted by the smoke scare. "Workers' efforts at the risk of their lives have made the situation progress little by little," Kan said, according to a government spokesman. But the head of the French nuclear safety agency, Andre-Claude Lacoste, warned that local contamination from the plant would continue to be a problem "for decades and decades". The natural disaster -- Japan's deadliest since 1923 -- has left 8,805 people dead and 12,664 missing, after entire communities were swept away by the horrific tsunami or levelled by the record quake. The World Bank said the disaster could cost the world's third-biggest economy up to $235 billion. That would be equivalent to 4.0pc of annual economic output, in an economy that has already been struggling for years. But growth should pick up in subsequent quarters "as reconstruction efforts, which could last five years, accelerate", the bank said in a new report on the Asia-Pacific region. Tokyo financial markets were closed on Monday for a national holiday. They took a pummelling for most of last week, driving global markets lower, before rallying on Friday when the G7 pledged currency intervention to curb the yen. Hopes of finding more survivors were dim 10 days after the twin disaster struck, despite one astonishing tale of survival with the discovery Sunday of an 80-year-old woman and her 16-year-old grandson. Their house in Ishinomaki city collapsed but the teenager was able to reach blankets, food and drink, helping them survive for more than a week, as they huddled together to keep warm in the region's freezing temperatures. The boy, Jin Abe, sounded frail as he spoke from his hospital bed on Monday in Ishinomaki, one of many places that felt the fury of the record quake and towering tsunami. "We found some water and snacks, so we ate them," he said. "We heard people outside but we couldn't escape."