Shanghai's food safety watchdog said on Thursday that it would continue its crackdown on substandard meat products, after nine restaurants were closed and hundreds more found to be violating food safety rules.

In an inspection of the city's 3,000 businesses serving meat products, more than 300 were found to have been exploiting loopholes in meat product sourcing or violating food safety regulations by failing to provide proper certification to show that their meat was qualified, said the Shanghai Food and Drug Administration.

The raid came amid concerns that rat, fox or mink meat, passed off as mutton, may have been served in Shanghai after police said earlier this month that a criminal ring producing and selling fake mutton had been broken up in nearby Jiangsu province.

As a result, the Shanghai Food and Drug Administration has pledged to severely punish the 180 involved businesses, the administration said, adding that another 150 businesses would be given a deadline to abide by the regulations.

Four businesses have been suspended from trading after they were found to be using mutton mixed with other meat or committed severe violations of food safety rules in raids that started earlier this month.

Another five, including one of P-Shang Dolar Hotpot's outlets in Nanhui district that was exposed by media as selling mutton mixed with meat from questionable sources, were closed due to food safety management problems.

The administration said that all of the city's 1,000 hotpot restaurants, where the fake mutton is mostly likely to have been used, have been screened in the inspection.

But that does not mean an end to the crackdown, Gu Zhenhua, a spokesman for the Shanghai Food Safety Office, said on Thursday. "Apart from hotpot restaurants, many other food businesses need to be checked."

He said that Shanghai, in accordance with the demand from the State Council, China's Cabinet, will continue to crack down on the illegal activities of producing and selling fake mutton and meat from animals that have died from diseases.

The State Council's food safety committee released a notice that demanded an in-depth overhaul of meat products and enhanced supervision of meat quality, Xinhua News Agency reported.

Rural areas, regions linking urban and rural areas, food companies' rented plants, workshops and warehouses are the main targets of the overhaul, the notice said.

It also told local governments to encourage tip-offs on food safety violations, protect whistleblowers and reward them well and in a timely manner.