Fukushima, Japan ? Japan announced the first signs that contamination from its tsunami-crippled nuclear complex has seeped into the food chain, saying that radiation levels in spinach and milk from farms near the facility exceeded government safety limits.

Japanese officials insisted that the small amounts of radiation — with traces also found in tap water in Tokyo — posed no immediate health threat, and said the situation at the Fukushima Dai-ichi plant, while still unpredictable, appeared to be coming under control after near-constant dousing of water to prevent spent fuel rods from burning up.

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.

Japan has been struggling with an overwhelming chain of disasters prompted by the 9.0-magnitude quake. The quake spawned a tsunami that ravaged Japan’s northeastern coast, killing more than 7,700 people and knocking out cooling systems at the plant, prompting overheated reactors and fuel to leak radiation.

More than 11,600 people are still missing, and more than 452,000 are living in shelters.

The government’s top spokesman, Chief Cabinet Secretary Yukio Edano, said at a news conference Saturday that tainted milk and spinach were collected from several farms ranging from 20 miles to 75 miles away from the reactors.

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 in a CT scan; for the spinach, it would be one-fifth of a CT scan. A CT scan is a compressed series of X-rays used for medical tests.

Minuscule amounts of radioactive iodine also were found in tap water Friday in Tokyo and elsewhere in Japan — 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.

An expert in the United States also said the risk from the radiation levels in food appeared limited and urged calm.

“The most troubling thing to me is the fear that’s out of proportion to the risk,” said Dr. Henry Duval Royal, a radiologist at Washington University Medical School.

The areas where the spinach and milk were sampled are rich farm country also 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.