The company that runs the plant, Tokyo Electric Power Co. (Tepco) sampled water about 100 metres south of the plant and found the level of iodine-131 was 126.7 times higher than government-set standards.
Caesium-134 was 24.8 times higher, and caesium-137 was 16.5 times higher, though a plant spokesman said Monday that the levels were not threatening to humans.
Shipments of milk and certain vegetables from areas around the plant have been suspended after high radiation levels were found in some products, according to a government spokesperson.
Grey smoke rose from reactor number three, according to Tepco. The cause of the smoke was not clear, but it took over two hours to clear. White smoke was later seen rising from reactor number two.
Fire trucks spraying water to help cool the reactors were disrupted by the smoke as well.
Before the smoke, Japan’s nuclear safety agency had said engineers were close to restoring some functions in the control room of reactor number two.
Yukiya Amano, the Japanese head of the International Atomic Energy Agency, the UN nuclear watchdog, said Monday that he had “no doubt” that the nuclear crisis could be overcome.
The head of the French nuclear safety agency warned, however, that local contamination would continue to be a problem "for decades and decades".