In the first sign that contamination from Japan's stricken nuclear complex has seeped into the food chain, officials said Saturday that radiation levels in spinach and milk from farms near the tsunami-crippled facility exceeded government safety limits.
Minuscule amounts of radioactive iodine also were found in tap water in Tokyo and elsewhere -- although experts said none of those tests showed any health risks.
The Health Ministry also said that radioactive iodine slightly above government safety limits was found in drinking water at one point Thursday in a sampling from Fukushima prefecture, the site of the nuclear plant, but later tests showed the level had fallen again.
Six workers trying to bring the Fukushima Dai-ichi plant back under control were exposed to more than 100 millisieverts of radiation -- Japan's normal limit for those involved in emergency operations, according to Tokyo Electric Power Co., which operates the complex. The government raised that limit to 250 millisieverts on Tuesday as the crisis escalated.
Emergency teams using an unmanned vehicle to spray water targeting the most at-risk of the plant's six reactors launched a new round today -- aimed at the plant's Unit 4 -- while preparing to switch power back on for the first time since a March 11 earthquake and tsunami knocked out the plant's crucial cooling systems.
However, there was no guarantee the cooling systems would still work, even once power was restored.
A replacement power line reached the complex Friday, but workers needed to methodically work through badly damaged and deeply complex electrical systems to make the final connections without setting off a spark and an explosion.
Officials said the crisis at the plant appeared to be stabilizing.
"We more or less do not expect to see anything worse than what we are seeing now," said Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency.
Japan has been grappling with a cascade of disasters unleashed by the 9.0-magnitude earthquake. The quake spawned a tsunami that ravaged Japan's northeastern coast, killing more than 7,700 people and knocking out cooling systems at the Fukushima Dai-ichi nuclear plant, causing the complex to leak radiation.
More than 11,600 people are missing. More than 452,000 are living in shelters.
Chief Cabinet Secretary Yukio Edano, meanwhile, insisted the contaminated foods "pose no immediate health risk."
The tainted milk was found 20 miles from the plant, an official said. The spinach was collected from six farms between 60 and 75 miles south of the reactors.
Those areas are rich farm country known for melons, rice and peaches, so the contamination could affect food supplies for large parts of Japan.
More tests were being done on other foods, Edano said, and if they show further contamination, then food shipments from the area would be halted.
Officials said it was too early to know if the nuclear crisis caused the contamination, but Edano said air sampling done near the dairy showed higher-than-normal radiation levels.
Iodine levels in the spinach exceeded safety limits by three to seven times, a food safety official said. Tests on the milk done Wednesday detected small amounts of iodine-131 and cesium-137. High levels of iodine are linked to thyroid cancer, one of the least deadly cancers if treated.
After the announcements, Japanese officials immediately tried to calm an already-jittery public, saying the amounts detected were so small that people would have to consume unimaginable amounts to endanger their health.
"Can you imagine eating one kilogram of spinach every day for one year?" said State Secretary of Health Minister Yoko Komiyama. One kilogram is a little over two pounds.
Edano said someone drinking the tainted milk for one year would consume as much radiation as he would in a CT scan; for the spinach, it would be one-fifth of a CT scan.
The Health Ministry said iodine levels slightly above the safety limit were discovered Thursday in drinking water samples from Fukushima prefecture. On Friday, levels were about half that benchmark; by Saturday, they had fallen further.
The trace amounts of iodine were found in Tokyo's water on Friday, the first day since the government ordered nationwide daily sampling due to the nuclear crisis, the Ministry of Education, Culture, Sports, Science and Technology said. A ministry statement said the amounts found did not exceed government safety limits.
At the Fukushima plant, emergency workers have been struggling to cool the reactors and the pools used to store used nuclear fuel, as well as put the facility back on the electricity grid.