Sanlu Group has recalled about 700 tons of its baby milk, after an infant diagnosed with kidney stones who was fed the food, died in Gansu province yesterday.

One of the country's largest dairy products' makers said its baby milk had been contaminated with a chemical called melamine. The announcement came after the company conducted an internal investigation.

A Gansu provincial health department spokesman said that altogether 59 infants have been diagnosed with kidney stones in the province this year. Reports said many of them had been fed the same brand of milk. No infants were diagnosed with kidney stones last year or in 2006 in the province.

Health experts said there is a link between melamine and kidney stones.

The first case was reported by the People's Liberation Army No 1 Hospital in Gansu's provincial capital of Lanzhou on June 28.

Similar cases have been reported from across the country - from the Ningxia Hui autonomous region, Gansu and Shaanxi to Jiangsu, Shandong, Anhui and Hunan provinces. But the total number of cases is not known.

Samples of the milk food were tested in a State-run laboratory,according to the country's food and drugs watchdog. The Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) launched a probe on Tuesday.

A spokesman for the Ministry of Health, which is helping with the investigation, said traces of cyanuramide that can cause kidney stones were found in Sanlu-brand milk products.

Earlier, Sanlu had said its products did not have any quality problems because they had passed State food safety tests. Yang Li, spokesman for the Shijiazhuang-based company, said a Sanlu team has left for Gansu to conduct its own probe.

Another Sanlu official said it was a possibility the baby milk may have been mislabeled, or “spurious products” are being sold under the company's brand, according to Xinhua.

Sanlu Group, based in Shijiazhuang, Hebei Province, is partly owned by New Zealand dairy export giant Fonterra Cooperative Group.

In a statement to the New Zealand Press Association, Fonterra said its Chinese partner was moving to ensure its products were safe.

Sanlu products have caused food scares before.. In 2005, Tianjin authorities seized hundreds of cases of mislabeled Sanlu yogurt.

Kidney stones are small, solid masses that form when salt or minerals normally found in urine crystallize inside the kidney. They can move out of the kidney if they become too big and cause infection, even leading to permanent kidney damage.

In 2004, at least 13 babies in Anhui province died after drinking spurious milk, which investigators later found had no nutritional value. The deaths rocked the country and triggered widespread probes into food and health safety.