Genetically modified rice is being sold in markets in the central Chinese province of Hubei, even though the authorities have not yet approved its sale in China, Greenpeace charged Wednesday.

Greenpeace employees were able to buy rice and rice seeds that had been modified to contain a bacteria, Bacillus thuringiensis (Bt), that produces a toxin that kills pests, Liu Haiying, program director for Greenpeace in Beijing, told reporters at a press conference.

China is testing several strains of genetically modified rice and is expected to approve one for commercialization this year.

Proponents of genetically-modified crops say they will improve yield and reduce plants’ vulnerability to pests. Opponents say pests will develop greater resistance to the modified crops, and that the techniques undermine biodiversity and could prove dangerous for human consumption.

Rice strains with Bt have been planted in China on a trial basis for several years as part of research conducted by Huazhong Agricultural University, in the city of Wuhan.

Liu said the Bt rice had been offered for sale at markets in Wuhan and a nearby suburb, and in two smaller Hubei cities.

“We haven’t sold the modified rice. We are still conducting trials,” said an assistant to professor Zhang Qifa, who is developing the Bt rice strain at Huazhong. She declined to speculate on how the rice had entered the markets.

Greenpeace estimated that 950 to 1,200 tons of the rice had been grown last year from a planted area of 1,900 to 2,400 mu. It estimates planted area this year at 20,000 to 25,000 mu with an output of 10,000 to 12,000 tons.