The number of infants on the mainland who have allegedly developed kidney stones after consuming Wyeth milk powder has risen to 20 but the US-based producer said it will pay for all medical expenses to determine the cause.

Wyeth said it has already received information about the babies and has contacted some of these families, National Business Daily reported on Thursday.

The company has already denied all the accusations but told the newspaper that it is willing to arrange more examinations for the families at other medical institutes to find out the actual cause of the kidney stones.

Families in Chongqing Municipality, Guangdong and Hubei provinces complained to the media that their children suffered from kidney stones because they had been drinking Wyeth milk formula.

Parents across the nation are very concerned after 22 domestic dairy companies were caught in September selling infant formula contaminated with melamine, a chemical added to make diluted milk appear to contain adequate protein. Milk powder from those products was blamed for the deaths of at least six infants and the cause of kidney stones and urinary tract problems in almost 300,000 others.

Wyeth said in a statement that all its products were produced with milk products from New Zealand and Australia and they had been proved safe after many checks.

The newspaper said that four of the affected families have received a 2,000-yuan compensation payment from authorities in Hubei Province.

However this has upset some of the families as the money was taken from a 1.1-billion-yuan compensation fund set up by 22 Chinese dairy companies and was not intended for compensation involving foreign milk brands, Li Xuefeng, one of the parents, told the newspaper.

Li, a father of a two-year-old boy in Chongqing, said his son had been given Wyeth milk formula since birth and was diagnosed with a stone in his left kidney last September.

Li said he would not ask for the 2,000-yuan compensation but would defend his family's rights through the law.

Officials at the Hubei Provincial Industrial and Commercial Bureau were reluctant to confirm the compensation payments.

The Shanghai Industrial and Commercial Authority told Shanghai Daily that the fund only covers patients who have been confirmed to have been affected by domestic milk brands.

The report said 90 percent of Wyeth's products sold in the Chinese market are imported from Singapore while the rest are processed at a factory in Shanghai.

The quality of foreign milk baby formula was questioned recently after 80 families across the country said their babies had kidney stone illnesses after using formula made by Shanghai-based Dumex Baby Food Co.

Dumex's reputation was quickly restored after health authorities confirmed that its products were melamine free.

Medical experts said there are many causes for kidney stones in infants.

Even if the child drank only one brand of milk powder, "it was still difficult to connect kidney stones directly with milk powder," said Dr Zhou Wei of the Shanghai Children's Medical Center.

(Shanghai Daily February 26, 2009)