CHANGSHA - Parents in a rural China town are frightened over claims of potential risks linked to genetically-modified (GM) food, as the government is continuing a probe into whether the town's children were used as guinea pigs for a US-China research program four years ago.

Dozens of children in the town of Jiangkou, located in Central China's Hunan province, are believed to have been fed modified "golden rice" as part of a nutrition research program led by a professor from the US's Tufts University in 2008.

Claims regarding the potential health risks of GM food - some of which appear to have been exaggerated - have triggered anxious speculation the parents of children attending the Jiangkou Central Primary School, where the experiments allegedly took place.

"Rumors are everywhere. Some say the kids may suffer from lung disease or lose reproductive capabilities when they grow up," said a parent surnamed Liu whose 11-year-old child allegedly participated in the test.

"I only learned the news a few days ago. I am very worried because it seems that no one can clearly explain what happened," said Liu.

Many of the parents have been frustrated by the progress of an official investigation launched in late August, as full results have yet to be announced. Some of the parents have tried to learn more about GM food on their own by searching for related news reports and information on the Internet.

Ministry of Health spokesman Deng Haihua on Tuesday urged the Chinese Center for Disease Control and Prevention (China CDC) to further investigate the case and publish their results in a timely manner.

The China CDC on Monday suspended a fellow researcher allegedly involved in the case for his "inconsistent accounts during the investigation." Government departments and research institutes have denied granting approval for the experiment.

Deng said the World Health Organization and the Council for International Organizations of Medical Sciences have formulated an international standard of ethics related to human biological medical research, adding that the Ministry of Health issued a regulation on human biological medical research in 2007 to strengthen research management.

GM food remains controversial nearly two decades after being introduced to the commercial market, as there is still no consensus on whether or not it is harmful to the human body.

Greenpeace, which informed the parents about the testing, said on its website that it is not known whether genetically engineered crops are safe for human or animal consumption. Independent scientific studies on the matter are severely lacking, it said.

"Until now, no government departments or institutes have publicly spoken about the health risks or lack thereof regarding GM rice. As parents, how can we rest assured?" said a parent surnamed He.

A government report issued by the National Development and Reform Commission last year said China needs to enhance the management of GM food safety, adding that the country's research into the food's toxicology remains in its initial stages.

"Although there is no sufficient evidence to show that it is dangerous, GM food is surrounded by uncertainties regarding its safety. More tests need to be done," the report said.

The report also urged the strict labeling of GM products and increased publicity regarding the products.

It is not yet known if the parents were told that the nutrition research program involved GM food, nor if the testing posed any health risks.

"I wish the claims about GM food health risks were only hearsay. I would be ashamed if anything bad happened to the children," said He Chongqiu, former principal of the Jiangkou school.