BEIJING — The number of children in China sickened by dairy products tainted with the banned industrial chemical melamine has jumped to nearly 53,000, the government said Sunday as it vowed to crack down on those responsible for one of China's worst food safety scandals in years.

More than 80 percent of the 12,892 children hospitalized in recent weeks were 2 years old or younger, the Health Ministry said in a statement posted on its Web site Sunday. Four children have died and 104 of the hospitalized children are in serious condition.

Another 39,965 children received outpatient treatment at hospitals and were considered "basically recovered," the ministry said.

The Health Ministry said that most of the hospitalized were sickened by powdered milk and baby formula. It said most of the sick children consumed baby formula from one company, the Shijiazhuang Sanlu Group Co., which is at the center of the scandal.

"The hospitalized children basically consumed Sanlu brand infant milk powder. No cases have been found from ingesting liquid milk," said the ministry statement.

Over the weekend, the Chinese territory of Hong Kong reported the first known illness outside mainland China — a 3-year-old girl who developed kidney stones after drinking Chinese dairy products. She was discharged from the hospital, the Hong Kong government said.

Singapore said Sunday that it had found traces of melamine in another Chinese-made dairy product, milk-based White Rabbit brand candy.

"Retailers and importers have been instructed to recall these products and withhold them from sale," Singapore's Agri-Food and Veterinary Authority said.

In the two weeks since the government first acknowledged the contamination, it has issued recalls for dairy products from 22 companies after tests turned up traces of melamine.

Melamine is used in making plastics and is high in nitrogen, which registers as protein in tests of milk. Though health experts believe ingesting minute amounts poses no danger, melamine can cause kidney stones, which can lead to kidney failure. Infants are particularly vulnerable.

Some of the farmers who sell milk to Chinese food companies are thought to have used melamine to disguise watered-down milk and fatten profit margins hurt by rising costs for feed, fuel and labor.

In Hong Kong, parents of the 3-year-old girl took her for a checkup because she had been drinking milk made by Chinese dairy Yili Industrial Group Co. every day for the past 15 months. Yili was among the 22 companies whose products were recalled for melamine contamination.

The ministry did not say why the number of cases had suddenly doubled from 6,200 on Saturday, but it suggested that health officials were combing through hospital records from May through August to trace the origins of the contamination. The deaths of three infants linked to tainted infant formula occurred in those months.

The Chinese government has launched high-profile efforts to show it is on top of the crisis, with Premier Wen Jiabao appearing on state-run television Sunday to say diary companies had to show more "social responsibility."

Wen was shown visiting a Beijing hospital where children were having health checks. He also stopped at a supermarket to look at dairy products.

"The government will put more efforts into food security, taking the incident as a warning," Wen said.

"What we are trying to do is to ensure no such event happens in future, by punishing those responsible leaders as well as enterprises. None of those companies lacking professional ethics or social morals will be let off," Wen said, according to the official Xinhua News Agency.

Since the problem of tainted milk products became public knowledge less than two weeks ago, the crisis has spread to include almost all of China's biggest dairy companies. Their products have been pulled from stores around the country, and in other places such as the self-governing Chinese territories of Hong Kong and Macau. Starbucks stopped offering milk in its 300 outlets in China.

Hong Kong's two main supermarket chains said Sunday they were recalling milk powder made by Swiss manufacturer Nestle after a newspaper reported it contains melamine.

Spokeswomen for both companies said they acted as a precaution after Hong Kong's Apple Daily reported Sunday that tests it commissioned showed that Nestle milk powder made in China's northeastern Heilongjiang province contained melamine.

Nestle's Hong Kong office did not immediately respond to a message seeking comment. Calls after work hours to its Beijing office and Beijing hot line went unanswered.

But the company said in a statement last Wednesday that none of its infant formula and milk powder products contained melamine.

"Nestle can hence assure its ... customers that its products are safe for consumption," it said.

Taiwanese company King Car Co. announced it has recalled packs of its Mr. Brown instant coffee and milk tea containing contaminated milk powder imported from China.

Japan and Singapore have recalled Chinese-made dairy products, and the governments of Malaysia and Brunei announced bans on milk products from China even though neither country currently imports Chinese dairy items.

The concern is because melamine has been found not only in powdered milk — used to make baby formula and other products — but also in liquid milk sold by China's biggest dairies.

Food and product safety scandals have been a feature of Chinese life. Only last year, the government promised to overhaul inspection procedures after exports of medicines, toys, pet food ingredients and other products killed and sickened people and pets in North and South America.

The chemical in the dangerous pet food was the same as in the milk scandal — melamine.


Associated Press reporter Min Lee in Hong Kong contributed to this report.