After three female infants in Wuhan, capital of central China's Hubei province, underwent abnormal sexual development, their parents blamed the manufacturer of the milk powder they had been using, while experts traced the source even further back in the food chain.

The infant underwent abnormal sexual development and her parent blamed the manufacturer of the milk powder they had been using.

In early July, the worried parents took their children to local hospitals for physical examinations, which showed that the babies' breasts were developing, the Beijing-based Health Times reported on Friday.

Medical tests revealed the hormones estradiol and prolactin in the babies exceeded those of the average adult woman.

The babies, who range in age from four months to 15 months, had been fed the same batch of infant formula produced by Syrutra, a Qingdao-based company, according to the report.

"The high amount of hormones in the babies definitely means there is a problem. The parents should stop using the formula to feed their children and the powder should be analyzed," Yang Qin, chief physician at the child health care department of Hubei Maternal and Child Health Hospital, was quoted as saying in the report.

When one parent requested that the formula be tested, the local administration of quality supervision, inspection and quarantine refused on the grounds that it only conducts tests for organizations, not individuals.

Meanwhile, hospitals, usually do not have the facilities or trained staff to perform such tests, according to the report.

In response to the issue, Syrutra posted a statement on its website over the weekend, in which it said: "We solemnly declare that the products produced and sold by Syrutra are safe. No man-made 'hormones' or any illegal substances were added during production."

Wang Dingmian, former chairman of the Guangdong Provincial Dairy Association, said it was highly possible for baby formula to contain sex hormones, though the source of the contamination needed to be traced back to the milk.

"It's not likely for the manufacturers to add hormones to their products, because it won't help them sell or pass any tests at all," Wang told China Daily on Sunday.

That does not mean the formula did not contain any hormones, he said, adding that the substance might have entered the food chain when the cattle were reared by farmers.

"Since a regulation forbidding the use of hormones to cultivate livestock has yet to be drawn up in China, it would be lying to say that nobody uses it," he said.

Although Syrutra declared that all of its raw materials were imported from overseas, Wang said it is possible there are loopholes in the current system, since China does not require raw materials imported for processing to be tested for hormones.

"It's reasonable to suspect the milk formula as a cause of the babies' early maturity given their simple diet. It is also possible that the mothers may have ingested the hormones during their pregnancies," he said.