The Sichuan Provincial Health Department confirmed on the weekend that an unknown disease had killed nine people and infected 20.

Hospitals in Ziyang city revealed that the patients had been infected by swine streptococcus suis bacteria that has also killed a large number of pigs.

It was reported that as many as 11 patients have died and 20 others are still hospitalized, with 10 in critical condition.

Secretary for Health, Welfare and Food York Chow said Sunday China's Ministry of Health notified Hong Kong Saturday about a ``widespread infection'' and that swine streptococcus bacteria was believed to be the cause.

``It is most likely that the streptococcus bacteria has been transmitted to humans and caused death,'' Chow said. ``We have to figure out whether it is a known bacteria or something else. Pig streptococcus bacteria is seldom transmitted to humans.''

Hong Kong imports frozen pork but not live pigs from Sichuan, and Chow said the pork sold in Hong Kong is safe to eat.

``Hong Kong imports certified frozen pork only from authorized exporters in the province, and the food safety of the pork can be absolutely guaranteed,'' he said.

Chow said there is no need to ban frozen pork from Sichuan. ``Sichuan is a big province, and we need to confirm whether the infections occurred in a single farm or farms in a larger area before coming to conclusion,'' he said.

Chow said there is no scientific evidence showing that imported frozen pork serves as a medium for the disease to transmitted to Hong Kong.

Ziyang Sihai Group, the biggest frozen pork exporter to the city, said their products are quarantined by the state, that they are not affected by the incident and will continue exporting to Eastern Europe and Hong Kong.

Chilled Meat and Poultry Association chairman Kwok Shi-hing said less than 20 percent of the imported frozen pork in Hong Kong came from Sichuan.

``We will temporarily stop importing from Sichuan,'' Kwok said. ``The supply will not be affected as we can make up shortfalls with imports from other provinces such as Shandong, Hunan and Guangxi.''

Hong Kong imports about 150,000 live pigs a month and only a small amount of frozen pork from the mainland.

``In the meantime, people who consume pork or other meat should thoroughly cook it before eating as this will kill most bacteria and minimize the risk of falling ill,'' Chow said.

Medical Association president Gabriel Choi said Hong Kong should be safe as long as the provincial authorities contain the spread of the disease within the province. ``The authorities should determine the route of the disease's transmission and make sure that frozen pork does not leave the province,'' Choi said, and suggested people do not travel to Sichuan until more is known about the outbreak.

Chow disagreed. ``There is no need to panic, Sichuan is a big province, and if travelers avoid going near farms and stay away from possibly sick animals, the risk [of being infected] is very low,'' he said.

Zhang Xuezhong, secretary of the Sichuan Provincial Communist Party Committee, told Chief Executive Donald Tsang Sunday that the epidemic is under control. Tsang was in Chengdu, the Sichuan provincial capital, to attend the second Pan-Pearl River Delta Regional Co-operation and Development Forum.

Infectious disease specialist Lo Wing-lok said the disease is common in pigs but there is a history of human infection.

``Where there are pigs, there is a chance of human infection,'' Lo said. ``The streptococcus suis bacteria is found in upper respiratory tract of pigs, in their nose and throat. Farmers exposed to doplets of swine saliva, and butchers who have open wounds when cutting the pork could be infected.''

Government statistics showed five people, mainly dim sum cooks, butchers and pork retailers, were infected with the disease in Hong Kong since last year.