Early Thursday, authorities arrested 12 more people in connection with the scandal, said Shi Guizhong, spokesman for the Hebei provincial police. The official said that brought the overall total detained to 18.
Police also confiscated nearly 500 pounds of melamine, the industrial chemical added to milk powder that has ignited a widening food safety crisis.
Health Minister Chen Zhu said Wednesday he expected the numbers of affected babies to increase as "more and more parents take kids to the hospital."
The head of China's quality control watchdog agency, Li Changjiang, said 5,000 inspectors will be sent out nationwide to monitor companies after government testing showed that 20 percent of the companies producing milk powder had dairy products with melamine.
The chemical additive was at the center of a pet food scandal in the United States in 2007. An estimated 1,500 dogs and cats died after ingesting a pet food ingredient manufactured in China that was laced with melamine.
The emerging crisis has raised questions about the effectiveness of tighter controls China promised after a series of food scares in recent years over contaminated seafood, toothpaste and pet food exports.
It is also the second major case in recent years involving baby formula. In 2004, more than 200 Chinese infants suffered malnutrition and at least 12 died after being fed phony formula that contained no nutrients.
In a sign of the government's concern, Premier Wen Jiabao presided over a meeting Wednesday of China's Cabinet to back plans for a national inspection of milk products, according to a notice on the government's Web site.
Suppliers to the dairy companies are believed to have added the banned chemical, normally used in plastics, to watered-down milk to make it appear higher in protein. Inspectors will now start testing for melamine in all dairy products, Li said.
On Wednesday, the country's two largest dairy companies, Mengniu Dairy Co. and Yili Industrial Group Co., were among the companies forced to recall baby formula. In addition, Guangdong-based Yashili and Qingdao-based Suncare recalled their tainted milk powder, which is exported to five countries in Africa and Asia: Bangladesh, Yemen, Gabon, Burundi and Myanmar.
U.S. authorities have said formula from China is not approved for import but may be on sale in ethnic groceries, especially areas with large Chinese populations.
Inspectors are checking for contaminated formula in U.S. stores, and U.S. Food and Drug Administration spokeswoman Judy Leon said none has been found. Inspectors have checked more than 500 stores in California alone.
"So that is good news," she said.
So far, all the sick infants in China were found to have consumed milk powder produced by the company at the heart of the crisis, Sanlu Group Co., Chen said. Most babies developed urinary problems, including kidney stones, after consuming Sanlu milk powder for three to six months, he said.
Sanlu's general manager Tian Wenhua, who was fired a day earlier, was detained by police Wednesday, the Xinhua news agency said.
China's health minister said that 6,244 babies fell ill after being fed tainted milk formula, and that 158 were suffering from acute kidney failure. Chen reported the death of a third baby in eastern Zhejiang province but gave no details. The two earlier deaths had been reported in Gansu province. Currently, 1,327 children, mostly newborns, remain hospitalized.
The political fallout continued Wednesday, with the mayor of Hebei province's capital, Shijiazhuang, being fired, Xinhua reported. Four other city officials from Shijiazhuang, where Sanlu is based, were fired earlier.
Sanlu company officials as well as government officials share the blame for delays in reporting the contamination, said Hebei Deputy Governor Yang Chongyong, who spoke on the sidelines of the press conference.
Sanlu did not inform the Shijiazhuang city government until Aug. 2, despite receiving public complaints about the milk powder five months earlier, Yang said. Then city officials waited until Sept. 9 to inform provincial officials, who then took a full day before contacting the central government, he said.
The company went public last week with the information after its New Zealand partner, Fonterra, told the New Zealand government, which then informed the Chinese government.
On Wednesday, Fonterra CEO Andrew Ferrier told reporters in New Zealand that Sanlu officials told the local government on Aug. 2 and urged an immediate public recall, but authorities "made their own judgment."
"We were enormously relieved when the Chinese government decided to make it public because we had been urging that from day one. The relief was just massive," he said.
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