“I’ve never seen anything like this,” clerk Toru Kikutaka said, surveying the downtown Tokyo supermarket where the entire stock of bottled water sold out almost immediately after the news broke, despite a limit of two, two-liter bottles per customer.

The unsettling new development affecting Japan’s largest city, home to around 13 million people, added to growing fears over the nation’s food supply.

Radiation from the Fukushima Dai-ichi nuclear plant has seeped into raw milk, seawater and 11 kinds of vegetables, including broccoli, cauliflower and turnips, from areas around the plant. The U.S. Food and Drug Administration said it was halting imports of Japanese dairy and produce from the region near the facility. Hong Kong went further and required that Japan perform safety checks on meat, eggs and seafood before accepting those products.

Officials are still struggling to stabilize the nuclear plant, which on Wednesday belched black smoke from Unit 3 and forced the evacuation of workers, further delaying attempts to make needed repairs. The plant, 140 miles (220 kilometers) north of Tokyo, has been leaking radiation since the quake and tsunami knocked out its crucial cooling systems.

The crisis is emerging as the world’s most expensive natural disaster on record, likely to cost up to $309 billion, according to a new government estimate. Police say an estimated 18,000 people were killed.

Concerns about food safety spread Wednesday to Tokyo after officials said tap water showed elevated radiation levels: 210 becquerels of iodine-131 per liter of water — more than twice the recommended limit of 100 becquerels per liter for infants. Another measurement taken later at a different site showed the level was 190 becquerels per liter. The recommended limit for adults is 300 becquerels.

“It is really scary. It is like a vicious negative spiral from the nuclear disaster,” said Etsuko Nomura, a mother of two children ages 2 and 5. “We have contaminated milk and vegetables, and now tap water in Tokyo, and I’m wondering what’s next.”

Infants are particularly vulnerable to radioactive iodine, which can cause thyroid cancer, experts say. The limits refer to sustained consumption rates, and officials urged calm, saying parents should stop giving the tap water to babies, but that it was no problem if the infants already had consumed small amounts.

“Even if you drink this water for one year, it will not affect people’s health,” Chief Cabinet Secretary Yukio Edano said.

Dr. Harold Swartz, a professor of radiology and medicine at Dartmouth Medical School in the U.S., said the radiation amounts being reported in the water are too low to pose any real risk, even to infants who are being fed water-based formula or to breast-fed infants whose mothers drink tap water.

Although the amounts are well above established limits, that doesn’t automatically mean there’s a health threat, he said.

“We live in a world that has natural background radiation that’s many times greater than the amounts we’re talking about here,” Swartz said.

Still, because it’s easy to avoid tap water, it makes sense for Japanese parents with infants to do so, he said.

Radioactive iodine is also short-lived, with a half-life of eight days — the length of time it takes for half of it to break down harmlessly.

Richard Wakeford, a public health radiologist at the University of Manchester in Britain, blamed the spike in radiation on a shift in winds from the nuclear plant toward Tokyo. He predicted lower levels in coming days once the wind shifts back to normal patterns. “I imagine that bottled water is now quite popular in Tokyo,” he said.

Tokyo’s municipal government said it would distribute 240,000 bottles of water to households with infants. They estimated that there are currently 80,000 babies in the affected area, with each infant getting three bottles of 550 milliliters.

Edano pleaded with shoppers to restrict purchases of bottled water to the bare necessity, urging them to think of tsunami victims in need.

“We have to consider Miyagi, where there is no drinking water at all,” he said, referring to a stricken region. “Under these conditions, we would appreciate it if people would avoid buying more water than they need.”

The latest data showed sharp increases in radioactivity levels in a range of vegetables. In an area about 25 miles (40 kilometers) northwest of the nuclear plant, levels for one locally grown leafy green called kukitachina measured 82 times the government limit for radioactive cesium and 11 times the limit for iodine.

The death toll from the disaster continued to rise, with more than 9,500 bodies counted and more than 16,000 people listed as missing.

Japan Nuclear Safety Commission Chairman Haruki Madarame said the government was “swiftly releasing information that is certain and not speculative” within Japan, but acknowledged it is behind in releasing information to foreign countries.”

Experts have said tiny radioactive particles, measured by a network of monitoring stations as they spread eastwards from Japan across the Pacific, North America, the Atlantic and to Europe, were far too low to cause any harm to humans.

“It’s only a matter of days before it disperses in the entire northern hemisphere,” said Andrea Stahl, a senior scientist at the Norwegian Institute for Air Research.

With supplies of fuel and ice dwindling, Japanese officials have abandoned the traditional practice of cremation in favor of quick, simple burials . Some are interred in bare plywood caskets and others in blue plastic tarps, with no time to build proper coffins. The bodies will be dug up and cremated once crematoriums catch up with the glut, officials assured families.

In Higashimatsushima in Miyagi prefecture, about 200 miles (320 kilometers) northeast of Tokyo, soldiers lowered plywood coffins into the ground, saluting each casket.

Some relatives placed flowers on the graves. Most remained stoic, folding hands in prayer. Two young girls wept inconsolably, hugged tightly by their father.

“I hope their spirits will rest in peace here at this temporary place,” said mourner Katsuko Oguni, 42.

Masaru Yamagata, a Higashimatsushima official, said the crematorium cannot keep up with demand.

“Giving the grieving families coffins is the most we can do right now,” Yamagata said. “Every day, more dead bodies are found, and we need more coffins quickly.”

The tsunami also heavily damaged the Fukushima Dai-ichi nuclear facility, with explosions and fires in four of the plant’s six reactors sending radioactive steam into the air.

Progress in cooling down the troubled plant has been intermittent, disrupted by rises in radiation, elevated pressure in reactors and overheated storage pools.

One of the workers was exposed to a high radiation dose that may increase the risk of cancer, a U.N. atomic agency official said Wednesday.

Japanese authorities have also told the International Atomic Energy Agency two prefectures near the crippled plant — Chiba and Ibaraki — were advised to monitor seafood products, the official, Graham Andrew, said.

Andrew said Japanese authorities had told the agency radiation dose rates at the plant were decreasing, but suggested iodine and cesium contamination in nearby areas had risen.

The IAEA also had information about 18 workers at the site which had been exposed to radiation since the accident, including one who got a dose rate of about 0.1 sieverts (106.3 millisieverts), although no medical treatment was required.

The agency did not say when it happened. The average dose for a nuclear plant worker is 50 millisieverts over five years.

The operator of Fukushima said last week it had raised the limit for the emergency work to 100 millisieverts an hour.

“The 0.1 sievert which you have there is certainly not a low dose and the individual may have a greater risk of certain cancer in the future…So it is something to be avoided, it is a high dose,” Andrew said.

The plant’s operator had restored circuitry to bring power to all six units and turned on lights at Unit 3 late Tuesday for the first time since the disaster — a significant step toward restarting the cooling system.

It had hoped to restore power to cooling pumps at the unit within days, but experts warned the work included the risk of sparking fires as electricity is restored through equipment potentially damaged in the tsunami.

And then on Wednesday, black smoke suddenly billowed from Unit 3, prompting another evacuation of workers from the plant in the afternoon, Tokyo Electric Power Co. officials said. They said there had been no corresponding spike in radiation at the plant.

Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency said officials did not know the reason for the smoke.

Tokyo Electric manager Teruaki Kobayashi said the pump for Unit 3 had been tested and was working Wednesday. But officials weren’t sure when they would be able to turn the power on to the pump.

Nuclear agency official Kenji Kawasaki said workers would not be allowed to return to the plant until Thursday morning, since smoke was still rising as of late Wednesday night.

As a precaution, officials have evacuated residents within 12 miles (20 kilometers) of the plant and advised those up to 19 miles (30 kilometers) away to stay indoors to minimize exposure.

And for the first time, Edano, the chief Cabinet secretary, suggested that those downwind of the plant should stay indoors with the windows shut tight — even if just outside the zone.

The Associated Press and Reuters contributed to this report.