China has launched a nationwide probe into all baby milk powders after a contaminant linked to the deaths and illness of thousands of pets in the United States last year was found in one brand.

Chinese authorities this week were investigating whether tainted formula led to the death of one infant and caused kidney stones in dozens of others, reviving memories of a fake formula scandal four years ago in which at least 13 babies died.

One baby died in northwestern Gansu province from kidney stones, a rare complaint in infants, and more than 50 others had developed kidney stones there and in other provinces this year.

Investigations showed that most of the babies had drunk Sanlu-brand formula, state media said.

The Sanlu Group, a Hebei province-based dairy producer partly owned by New Zealand dairy export giant Fonterra Co-operative Group Ltd., issued an immediate recall of milk formula made before August 6, saying about 700 tonnes of melamine-contaminated powder were in circulation, Xinhua said.

Calls to the company went unanswered.

Melamine, used as an ingredient in plastics, fertilizers and cleaning products, has been used by Chinese suppliers of animal feed components to make protein levels appear higher than they are in quality testing.

"If you put it through tests, it will give a false reading to lead you to think the protein content is higher than it actually is," said Allen Chan, an associate professor in chemical pathology at the Chinese University of Hong Kong.

Melamine-contaminated ingredients sourced from China for use in pet food were linked to kidney failures and kidney stones in thousands of cats and dogs in the United States last year.

Kidney stones are small, solid masses that form when salts or minerals normally found in urine crystallise inside the kidney. If they become large enough, they can move out of the kidney, cause infection and lead to permanent kidney damage.

China's quality watchdog, the Administration of Quality, Supervision, Inspection and Quarantine (AQSIQ), had launched a probe into all baby milk producers, Xinhua said.

"The results (of the investigation) will be announced to the public in a timely manner," AQSIQ said in a statement.  The World Health Organisation said it was in close consultation with Chinese health authorities.

"We are monitoring the situation in China and for potential wider implications for other countries," WHO China representative Hans Troedsson told Reuters in an emailed statement.
    It was unclear whether any of the formula had been exported.

The United States' Food and Drug Administration warned consumers on Thursday not to buy or use baby formula from China, which is banned in the United States.

The health scare broke after Xinhua quoted doctors at a hospital in China's northwestern Gansu province as saying that "fake milk powder" from one brand could have been responsible for kidney stones developing in 14 patients, all under 11 months.

The problem formula had been sold in mainly poor and remote regions at much lower prices than usual, Xinhua said, citing parents whose children were affected.

Parents in Beijing returned Sanlu formula to supermarkets. "When we heard about this problem last night, we did not sleep well," said Diao Long, the father of a baby daughter who had drunk Sanlu for the past six months. "We are really worried there could be serious side-effects for our child." - Reuters