Shanghai food safety officials have ordered the closure of all the nine cooked food stores that were supplied with fake mutton by a gang in neighboring Jiangsu Province.

The fake mutton was seized and destroyed by police in Jiangsu's Jiangyin City in January and February after investigation into the gang. But local food safety officials were unaware of the situation until the Ministry of Public Security announced details of the crackdown on its website last week.

All products being sold from the stores are now being checked. One of the stores had already closed but eight were still in operation.

A chief suspect, surnamed Wei, is said to have been selling frozen cooked fake mutton to the nine cooked food stores in Shanghai wet markets since 2010. "Wei even granted the stores credit if the store owners seem reluctant to buy his frozen mutton," Yan Zuqiang, director of the Shanghai Food Safety Office, said yesterday.

Wei, a native of Jiangyin, is said to have used meats from foxes, mink and rats to make "mutton" by mixing the meats with gelatin, salt and coloring agents.

The nine stores involved were not large, occupying a space of just eight to 10 square meters each in small wet markets and run by 10 migrant workers.

The case involved over 70 kilograms of "mutton," which Wei sold to the cooked food stores at 22 yuan (US$3.49) to 24 yuan per kilogram. Jiangyin police have interviewed all the store operators and two of them, surnamed Zhong and Qian, are on bail awaiting trial.

"While cooperating with Jiangyin police in the case, the local authority will also impose punishment on the store owners," Yan said.

Two of the stores, which did the most business, will be investigated by Shanghai's commercial and industrial administrative bureau for violations of food safety laws.