'No connection'

"No banned additional sex hormones were found [in the Synutra samples]'' and naturally occurring hormones in the milk were within normal ranges, he said.

The ministry tested 42 samples of Synutra milk, including some from the families' homes in Hubei, and 31 samples from other Chinese and foreign suppliers.

A ministry "experts group'' concluded breast growth in the three Hubei cases "has no connection to the Synutra milk powder,'' he said.

A fourth case was reported in Beijing, Xinhua news agency reported on Tuesday.

The ministry said previously that medical experts were assisting a separate investigation into the cause of the infants' condition.

The babies went through "mini-puberty'' but their bones and body size are normal for their age, Wu Xueyan, director of endocrynology for Peking Union Hospital, said.

"Normal physical range'

The breast growth is "within normal physical range'' and less than what would be caused by large amounts of external estrogen, the female sex hormone, Wu said.

Tests indicated the level of hormones in three girls, ranging in age from four months to 15 months, who were fed the formula exceeded those of the average adult woman, the China Daily reported last week.

Chinese dairy products were recalled worldwide in 2008 after it was found that melamine, which is used to make plastics, was widely and illegally added to the products to give the appearance of higher protein.

Melamine was found in the products of 22 Chinese dairy companies in a massive scandal blamed for the deaths of at least six infants and for causing 300,000 others to fall ill.