SHIZUOKA, Japan | The government Wednesday warned Tokyo residents against giving tap water to babies, after discovering double the level of radiation considered safe for infants, as the damaged nuclear power plant in northeastern Japan belched black smoke from an unknown source.
Japan also said the economic damage from the March 11 earthquake and tsunami could be as high as $309 billion, making the catastrophe the world's most expensive natural disaster.
Anxiety levels in Tokyo soared, after officials added tap water to precautions on fresh milk and vegetables from the region near the Dai-ichi nuclear power plant in Fukushima prefecture, about 150 miles northeast of the capital.
"It is really scary. It is like a vicious negative spiral from the nuclear disaster," said Etsuko Nomura, a mother of children ages 2 and 5. "We have contaminated milk and vegetables, and now tap water in Tokyo, and I'm wondering what's next."
Neighborhood loudspeakers across the greater Tokyo area blared messages about contaminated drinking water.
Tokyo Gov. Shintaro Ishihara said water could be used with no immediate risk for adults.
"But, for infants under age 1, I would like them to refrain from using tap water to dilute baby formula," he added.
The Tokyo Water Bureau found levels of radioactive iodine-131 rose to 210 becquerals per quart of tap water, more than double the limit for infants but well below the safe level of 300 for adults. A becqueral is an international unit measure of radioactivity.
The temporary ban on 11 types of winter vegetables from Fukushima prefecture means farmers will lose most of their winter crops now due for harvesting.
Laboratory tests also suggest that the soil might be too contaminated for spring planting, which could exacerbate Japan's acute shortage of food. Seafood, a staple of Japanese diets, is also in short supply because the tsunami wiped out ports and fishing boats in the hardest hit areas.
Government spokesman Yukio Edano warned against panic-buying and hoarding of water, as he tried to soothe the rattled nerves of Tokyo's 13 million residents.
"Even if you drink this water for one year, it will not affect people's health," Mr. Edano said, referring to older children and adults. "Even if these foods are temporarily eaten, there is no health hazard."
Many consumers on Twitter and Facebook sites said their local supermarkets are rationing bottled beverages, including water and tea, to one bottle per customer, as people hurried to stock up on dwindling supplies.
"I've never seen anything like this," said a befuddled Tokyo store clerk, looking at empty shelves cleared of bottle water within minutes of the announcement about tap water.
The U.S. Food and Drug Administration blocked imports of vegetables, milk and fruit from Fukushima, Ibaraki, Tochigi and Gunma prefectures, while Asian countries stepped up tests of food imported from Japan, and Taiwan warned its fishermen to avoid Japanese waters.
At the power plant in Fukushima, black smoke billowed from one of the six nuclear reactor units.
"We don't know the reason," said Hidehiko Nishiyama of Japan's Nuclear Safety Agency.
• This article is based in part on wire service reports.
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