Four positive samples were discovered at the abattoir in Shuangcheng by a local flu laboratory, China News Service quoted a ministry statement as saying.
Officials suggested the cause of infection could have been the animals´ close contact with humans during transportation.
Gene sequence analysis showed the virus suffered by the pigs is a 99-per cent match with the human H1N1 strain. No mutation was found, the government statement said.
It is the first such infection in China, although there have already been reports in 13 other countries and regions