BEIJING - Chinese health officials are investigating a growing number of cases of kidney stones in babies, state media said Thursday, months after a tainted milk scandal in which hundreds of thousands of children who drank melamine-contaminated formula suffered similar ailments.

While the Health Ministry has not directly linked the new cases to dairy products, parents are blaming formula made by Dumex Baby Food Co. Ltd., a subsidiary of France's Groupe Danone SA. Dumex insists that its products are safe, and health officials said tests showed they are free of melamine, an industrial chemical.

The China Daily newspaper said Thursday that the Health Ministry has asked all local health bureaus to begin epidemiological research on kidney problems in children, including checking their eating habits and living environment.

"We're trying to find out why the number of kidney ailments among babies has risen drastically," Ma Yangchen of the ministry's press office was quoted as saying. The report did not say how many children have become sick, when they became ill or what triggered the investigation.

A woman who answered the telephone at the Health Ministry said there was no official statement on the matter.

The ministry's investigation reflects government efforts to restore public confidence after milk tainted with melamine, used in the production of plastics and fertilizer, was linked to the deaths last year of at least six Chinese babies and illnesses of nearly 300,000 others.

The scandal, which unfolded in September, was one of the country's worst food contamination crises. It involved the products of China's biggest dairies and underscored the government's problems with policing product quality.

State media have said that officials started looking into Dumex because of overseas media reports last month that about 48 Chinese babies suffered kidney-related illnesses after drinking the company's milk. It did not identify the reports.

Dumex has insisted that all its products are safe. The Shanghai Municipal Bureau of Quality and Technical Supervision said over the weekend it had tested 932 batches of dairy products produced by the Danone subsidiary since mid-September "and all are melamine-free."

It also said no melamine was found in more than 1,700 batches produced before mid-September, when the dairy scandal broke.

Dumex's main China office in Shanghai had no immediate comment Thursday.

Jiang Yalin, a mother in the southwestern province of Guizhou and the leader of a parents' group, said her daughter drank only Dumex milk after she turned 1 and fell sick about two months later. She cried constantly at night, even in her sleep, and started having problems urinating, Jiang said.

When Jiang took her daughter to the hospital in September after reading about the tainted milk scandal, doctors said the child had stones as big as rice grains in both her kidneys.

"I was stunned. I felt helpless and angry," Jiang said in a telephone interview.

The girl has since recovered and Jiang says doctors have declared her healthy.

Jiang said she has compiled a list of more than 100 babies - the youngest only a couple of months old - who fell sick after drinking Dumex and may file a suit against the company.

"I must figure out what exactly it was that harmed my daughter. I must know," Jiang said.