Authorities in Hunan province on Saturday denied that children in a rural school were guinea pigs in a US research project on the effects of genetically modified rice.

A girl stands next to a paddy field. A Greenpeace report says 24 Chinese kids have been used for a U.S. GM rice experiment.

A research paper involving 68 Chinese primary-school children in the province was published by the American Journal of Clinical Nutrition on Aug 1, with Guangwen Tang at Tufts University in the US named as the lead author.

The unapproved experimental GM rice, widely referred to as "golden rice" and genetically engineered to produce provitamin A, was created by Ingo Potrykus at the Institute of Plant Sciences in the Swiss Federal Institute of Technology and Peter Beyer at the University of Freiburg more than 10 years ago.

Chen Peihou, deputy director of the Hunan Center for Disease Control and Prevention, confirmed that the second author of the paper, listed as Hu Yuming, is a researcher for the center.

"I was aware of the project in Hengyang in 2008, which involved children and was mainly testing for beta-carotene bioavailability and bioconversion to retinol," or vitamin A, Chen said Sunday. "But as far as I know, no GM rice was used, and all the food involved was locally produced."

He also said that Hu was not asked by the journal to sign the paper before its publication.

"In the project, we just provided the site and assistance to the Chinese Center for Disease Control and Prevention, and we have not dealt with any US institution," he added.