A preliminary investigation confirmed the contaminated Sanlu baby milk powder as the cause of kidney stones in infants after a first-phase probe by experts, China's Ministry of Health said on Friday.

An investigation team jointly organized by departments including the health, public security, agriculture ministries and quality watchdog examined the urine and kidney stones of the infant patients and found the substance melamine therein.

The investigation team, which is in Shijiazhuang, Hebei Province, where dairy producer Sanlu Group is based, is now coordinating with the local government to investigate the incident.

"Those responsible for the contaminated milk will face severe punishment," said an official with the team.

The team arrived in Hebei on Friday. After listening to the local government's report on its handling of the incident, they collected samples and documents from the Sanlu Group and the local quality testing agency. They also visited the affected babies in local hospitals and gave advice on the treatment.

Sanlu, one of China's leading dairy producers, found during an internal company investigation in August its powdered milk products were contaminated with melamine, according to the team's investigation.

The statement didn't say why the company didn't release the findings until news reports exposed dozens of babies became sick with kidney stones after consuming the Sanlu brand of baby milk powder for a prolonged period.

Health experts said melamine is a chemical raw material. Ingestion can lead to stone formation in the urinary tract.

A thermosetting plastic, melamine has an appearance similar to milk powder. It is widely used in manufacturing fabric, glue, housewares and flame retardants.

"The substance gives the appearance of a high nitrogen level, which is an index to measure the protein content in food," a health expert told Xinhua. He declined to be named.

One baby in the northwest Gansu Province died from the stones. At least 59 cases had been reported in Gansu and other provinces.

Sanlu had sealed off 2,176 tonnes of contaminated milk powder and recalled 8,210 tonnes from the market. There were still 700 tonnes in circulation. All the contaminated formula was produced before Aug. 6.

Supermarkets in some provinces had started to pull the milk powder off shelves.

The Health Ministry said on Friday it had launched a nationwide investigation into the contaminated milk formula. All local health agencies were to report cases of infants with kidney stones immediately. It also issued a treatment plan on its website (www.moh.gov.cn) to help hospitals deal with sick babies.

(Xinhua News Agency September 13, 2008)