The official Xinhua News Agency reported Saturday that the dairy, Sanlu Group Col, was ordered to stop production as the number of sick babies rose to 432.
A Health Ministry statement gave no indication why Sanlu Group Co., China's biggest milk powder producer, failed to warn consumers immediately. Employees who answered the phone Saturday at the ministry's news office and at China's product safety agency said they had no more information.
In August, Sanlu's testing revealed melamine in the milk powder, a ministry statement said. Melamine is a toxic chemical used in plastics that contaminated pet food last year.
The ministry did not say when Sanlu alerted authorities about its findings but the dairy ordered a recall Thursday of 700 tons of formula made before Aug. 6.
A New Zealand dairy cooperative that owns part of Sanlu said Friday it believed none of the tainted powder was exported.
Kidney problems in infants were reported as early as mid-July but authorities failed to launch a food safety investigation, Xinhua said in a separate report. Another news report said the dairy received complaints as early as March.
Investigators are questioning 78 people about the contamination, which occurred when dairy farmers added melamine to the milk, possibly to make its protein content appear higher, Xinhua said. Melamine is rich in nitrogen and standard tests for protein in bulk food ingredients measure nitrogen levels.
The incident reflects China's enduring problems with product safety despite a shake up of its regulatory system following a spate of warnings and recalls about tainted toothpaste, faulty tires and other goods.
The biggest group of victims is in China itself, where shoddy or counterfeit products are common. Infants, hospital patients and others have been killed or injured by tainted or fake milk, medicines, liquor and other products.
The number of infants suffering kidney stones after being fed Sanlu formula has risen to 432, Xinhua said. It did not give a breakdown of where in China the cases were.
Xinhua cited a Gansu provincial health department spokesman as saying he received reports on July 16 that 16 infants under a year old, all of whom drank Sanlu milk, were suffering a rare kidney ailment. He said the Health Ministry launched an epidemic survey.
"However, there seemed no food and safety survey had been done. Otherwise, the health, and even lives, of many infants could have been saved," Xinhua said.
A Sanlu manager quoted by the newspaper Beijing News said the dairy received complaints in March and June but could not track down the problem.
Another Sanlu manager quoted Friday on the Web site of a leading Chinese business magazine, Caijing, said it refrained from making an announcement because some grocers refused to return tainted powder. The report did not say why that prevented a warning.
