Zhang Jiuying, a public relations director with Syrutra, told Xinhua after the Health Ministry press conference that the company also hopes authorities publish the test results as soon as possible.

On its official website, Nasdaq-listed Syrutra said in a statement that it had never added man-made hormones or any other illegal substances to its milk products, and that all its products were safe.

It said it was planning to sue Phoenix TV, which was among the first and most persistent media to report the Syrutra hormone suspicions, for "fabricating lies that the milk powder had led to premature puberty, deceiving the consumers, discrediting the company, and interfering with its normal businesses."

The Syrutra-brand milk powder is still on the shelf at a Carrefour Supermarket in Wuhan, but its sales have fallen.

"Sales of the product has dropped by more than 10,000 yuan (1,476 U.S. dollars) over the past month," said a saleswoman at the supermarket.

Syrutra's stock prices at Nasdaq fell by almost 27 percent on Monday.

The statement said it was "unscientific and unreasonable for some media to blame premature puberty on the milk formula."

Syrutra's claim was backed by some experts.

Yao Hui, deputy head of the endocrine department of Wuhan Children's Hospital, said among the latest cases treated for the condition at the hospital, three of the four children had never eaten baby formula made by Syrutra. The other baby used to eat Syrutra formula, but switched to other brands last year.

Wang Dingmian, a council member of the Dairy Association of China also said it was unlikely dairy firms would add hormones to baby formula.

Unlike the melamine case, dairy companies would gain no commercial benefit from adding hormones to its products, Monday's Beijing Times quoted Wang as saying.

But that did not make the milk formula hormone-free, Wang said, adding the substance might have entered the food chain when cattle were reared by farmers.

He said dairy firms should have conducted thorough checks on the raw milk sources.

According to Syrutra's website, the company imports raw dairy materials from Europe and New Zealand. All the materials have passed quarantine inspections by the exporting country and China, and met international and Chinese quality standards, it said.

But Chinese parents have obviously lost faith in the milk industry. Tuesday's Beijing Times quoted a doctor from Beijing Children's Hospital as saying that many parents had brought their infant daughters to check for premature puberty in the past two days.

But the doctor said she had not seen any cases caused by external factors, the paper said.

The event came as another blow to the fragile credibility of China's dairy industry.

The industry was hammered in 2008 when milk laced with melamine, a chemical added to milk products to make their protein content seem richer, sickened 300,000 children and killed six.