The Ministry of Agriculture's statement came three days after a Chinese scientist said pigs had been found last year to be infected with the deadly H5N1 strain of bird flu.

Chen Hualan told a forum on Friday that pigs in southern Fujian province were infected for the first time with H5N1 in 2002 and 2003, but did not provide details.

Scientists fear that human and bird flu viruses could mix in pigs and form a strain more easily transmittable to humans.

The ministry, which did not directly refute Chen's claim, said it found no infected pigs when it conducted tests early this year in the midst of a bird flu outbreak in the southern provinces.

"Related departments have already informed the U.N. Food and Agriculture Organization, the World Health Organization and other international groups, as well as sent reports to Hong Kong, Macau and Taiwan," the ministry said on its Web site, www.agri.gov.cn. WHO health experts said on Saturday Chen's findings were not conclusive and did not mean H5N1 easily crossed over into mammals.

"This is a complex story, there are many chapters in this book, and the pigs are another potential chapter. It's not linear and there are many characters," Julie Hall, a WHO disease control expert based in China, told Reuters.

Shigeru Omi, WHO's regional director for the Western Pacific region, said he hoped the Chinese authorities could discuss the matter "in an open manner".

"This kind of information should be shared by all the people concerned," he said. "The collaboration between the Chinese government and the WHO has been transparent and very open so I hope the same kind of spirit would also apply to the Ministry of Agriculture."

Source: Reuters - 23rd August 2004