Agriculture Department officials cautioned that further tests were needed to confirm that the pigs had been infected with H1N1. Officials said that the pigs did not exhibit signs of sickness and may have been exposed to a group of children who had contracted the swine flu virus.
Samples from the pigs that may have tested positive were collected at the Minnesota State Fair between Aug. 26 and Sept. 1. USDA officials did not say how many pigs may have tested positive.
Agriculture Secretary Tom Vilsack said testing is under way and results should be available in a matter of days. He said the USDA is working with the Centers for Disease Control and Prevention.