China's national grain reserves may be polluted by genetically modified (GM) rice after tainted rice was discovered in Central China's Hubei province, Greenpeace representatives warned on Tuesday.

A young man raises a placard that reads "No genetically modified (GM) food" outside a supermarket in the Zhongguancun area of Beijing on Sunday to protest against some factories promoting GM food. [Photo / China Daily]

Lorena Luo, a food and agriculture specialist with non-governmental environmental organization Greenpeace, said its monitors found three distinct GM-positive rice samples produced in 2007 by two grain processing companies in the Hubei capital of Wuhan.

"In April, we bought three rice samples weighing 1,200 grams in Wuhan - all of which has been tested as GM at a qualified lab in Hong Kong," Luo told reporters on Tuesday.

The test results indicated the rice was developed from one of the two strains of pest-resistant GM rice, which was cultivated by the Wuhan-based Huazhong Agricultural University and was issued with bio-safety certificates by the Ministry of Agriculture last August.

Luo, however, declined to name the Hong Kong-based laboratory.

"Most grains in our company were coming from nearby State-owned grain depots as well as the national grain reserve," an unidentified worker at the Guocheng Rice Company, one of the two companies with the tainted rice samples, testified in a video provided by Greenpeace.

"If true, the report will be a serious problem, as GM rice in the national grain reserves could spread into other places," Lu Bu, a researcher from the Institute of Agriculture Resources and Regional Planning at the Chinese Academy of Agricultural Sciences, told China Daily on Tuesday.