'Ample reserves'

One direct result of the salt rush was reflected in the stock market. When it opened on Thursday, the share prices of Yunnan Salt & Salt Chemical Co. rose by 10 percent, the maximum fluctuation range allowed in a day by Chinese exchange rules. It closed with a 9.98 percent jump from the day before.

On the same day, China's top economic planner ordered a crackdown on hoarding of daily necessities.

The National Development and Reform Commission said in an urgent notice issued Thursday that local price control authorities should counter rumors about shortages of daily necessities and hoarding of these goods.

It also pledged ample supplies of daily necessities including salt, saying it would work with relevant agencies to meet market demand and maintain price stability.

China Salt also tried to relieve public concern Thursday, saying the country has substantial salt reserves to meet the demand for the product.

Only 20 percent of China's salt comes from the ocean. Most salt on sale is rock salt, which is mined.

"We have ample salt reserves to meet people's needs, and panic buying and hoarding are unnecessary," China Salt said in a statement released to Xinhua News Agency. "China has an annual salt production capacity of more than 80 million tons, but the country's consumption of edible salt was about 8 million tons a year."

The Ministry of Health posted information on its website, telling people that taking regular table salt cannot prevent radiation illness. An adult would need to ingest 3 kilograms (6.61 pounds) of salt at one time to help prevent health effects from radiation, the ministry said.

Potassium iodide pills are used to help mitigate the effects of radiation, but regular table salt doesn't contain enough iodine to block the poisoning, according to health experts.

'Rumors are harmful'

The Chinese government also weighed in Thursday, with Foreign Ministry spokeswoman Jiang Yu saying, "I do not see any necessity to panic."

In its notice, the Development and Reform Commission also urged local authorities to take "immediate action to monitor the market prices and resolutely crack down on illegal acts, including spreading rumors to deceive the public".

Michael O'Leary, WHO's representative in China, called on governments and individuals to "take steps to halt these rumors, which are harmful to public morale".

O'Leary said WHO "would like to assure governments and members of the public that there is no evidence at this time of any significant international spread from the nuclear site".

Su Xu, a researcher with the Chinese Center for Disease Control and Prevention, said that iodized salt would do little to help protect against radiation and warned that taking excessive amounts of iodine was harmful.

"Iodine drugs should be used only under the medical supervision of doctors and medicine specialists," he said.

Others worry the phenomenon showed just how far people's trust in official information has diminished.

AP, Reuters and Cao Yin contributed to this story.

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