More Chinese provinces have banned the sale of cowpeas grown in south China's Hainan province as concern about "toxic cowpeas" spreads.

China's Ministry of Agriculture issued an urgent circular Wednesday concerning the safety and monitoring of vegetable production processes.

Cowpeas nationwide were tested for Isocarbophos, a highly toxic pesticide, after the pesticide was detected in Hainan-grown cowpeas on sale in markets in central China's Hubei province and east China's Anhui province.

In Jiangmen city, Guangdong province, more than nine metric tons of toxic Hainan-grown cowpeas were discovered, 5.8 tons of which had been sold. The other 3.75 tons was destroyed.

Guangdong authorities banned further sales of Hainan cowpeas and urged Jiangmen vegetable markets to track down the already sold cowpeas.

In Chengdu, capital city of southwest China's Sichuan province, even though tests found no toxic pesticides, many supermarkets stopped selling cowpeas and destroyed all cowpeas from Hainan.

"We started refusing cowpeas from Hainan about a month ago, just to be safe," a spokesperson for Chendu's Haoyouduo supermarket said.

So far, seven supermarkets in Chengdu have destroyed 25 kg of Hainan cowpeas.

In north China's Shanxi province, tests on cowpeas were also conducted.

"We immediately tested Hainan cowpeas in the province after we read the reports on the Internet," said Xu Shan, vice director of the Consumer Protection Department in Shanxi's provincial industry and commerce bureau.

"As of 11:00 am Friday, no toxic cowpeas had been found, but we'll continue to monitor the situation," Xu said.

About 80 percent to 90 percent of Hainan-grown cowpeas are sold to other Chinese provinces, said Chen Wenhe, director of the Plant Cultivation Management Department in the Hainan Provincial Agriculture Bureau.

"Some 113 boxes of cowpeas sent to Shanghai on February 19 were found to be contaminated with Isocarbophos. They then refused 500 boxes," Lu Jinhu, a Hainan cowpea dealer said.

"I'm not doing any cowpea business now, since no one's willing to buy them," he said.

Hainan has taken measures to boost vegetable safety, officials said on Thursday.

Hainan's Sanya city has allocated 200,000 yuan ($29,282) for local agriculture bureaus to increase monitoring.

Still, experts said it is the farmers who should realize the importance of vegetable safety.