Unsafe artificial green peas were found in Hunan province earlier this month, making the list of toxic food products in the country even longer, according to the local food safety watchdog.

The problematic green peas appeared in the provincial capital of Changsha and Hengyang city, a local newspaper reported over the weekend.

"The peas were an unnatural color and had a penetrating odor. After 20 minutes of cooking, the peas did not turn soft but the water turned green," the report said.

The peas were first seen on March 17 during a regular pesticide residue check in a Changsha farmers' market. From March 17 to 19, local food safety officials conducted field research and sourced the peas back to Hengyang.

Last Wednesday, officials from the Hengyang law enforcement team on agriculture smashed up two small illegal workshops where the peas were made.

A video provided by a local TV station showed the manufacturing process of the peas.

Bags of dried snow peas and soybeans were thrown into water-filled jars. With the help of light green colorant and sodium metabisulfite, a food additive used as a bleach and preservative, the previously wizened dry peas came out plump and fresh green.

However, the use of the light green colorant is forbidden in farm products, since it could cause cancer, the report said. Similarly, excessive intake of the sodium metabisulfite can hinder the human body's absorption of calcium.

The processing of the peas is highly profitable, said Peng Xingguo, owner of one such illegal workshops. Peng's workshop had been running for three years before it was exposed.

"One jin (0.5kg) of snow peas could turn to 1.7 jin after processing, and 1 jin of soybeans would be 1.8 jin. I can make 1.5 yuan (20 cents) with each jin of the green peas processed. About 1,000 kg are sold every day," Peng said in the video.

The news is not new, as similar media reports appeared in 2005, 2006 and 2007, said Sang Liwei, a Beijing-based food safety expert.

"Such toxic artificial green peas have been found in Hunan and Guangdong before, but it looks like the news didn't catch enough attention from the officials," Sang said on Monday.

In China, officials call it a "food safety incident" only after a death is reported.

"In cases like this, where the danger only lies in possible long-term diseases caused by the misuse of additives, it's not surprising to see lagged handlings," he said.