About 160 piglets of up to five weeks old were coughing and showing other typical flu virus symptoms such as runny noses, reports said.

The virus was found during tests of three animals after they died of other causes late last month, officials said. The farm counts 3,000 animals but only about a hundred showed the symptoms of the flu virus.

The Council of Agriculture said the type of virus found in the pigs was for 97.5 percent the same as the A (H1N1) virus, apparently confirming the theory that humans had infected the animals.

Health officials visited the farm Thursday to disinfect the premises and take tests from both the animals and the seven people employed on the site. Preliminary results indicated none of the farm workers were infected, reports said, but they were asked to stay at home.

One of the farmers had visited China and felt unwell after his return, but he was not believed to have contracted the virus, officials said.

Earlier, the farm had already been closed off to prevent the virus from contaminating other farms and residents. The authorities issued a ban on the sale of the pigs, and began investigating other pig farms within three kilometers from the site of the infection. No cases of swine flu were reported from pig farms elsewhere in the country.

The animals at the Taitung farm were likely to recover within three to seven days, the COA said. Nine other countries, including the United States and Japan, had reported similar infections of pigs by humans before, but no transfer of the virus in the other direction, experts said.

The COA insisted consumers of pork were not running any risk of infection from eating the meat.

World Health Organization experts have expressed the fear that the A (H1N1) virus might mutate into a new form and spread from animals to people.

Taiwan started its inoculation campaign against the swine flu virus earlier this week.