Final tests confirm that six pigs from the Minnesota State Fair contracted swine flu, three more than initial research had indicated.

The U.S. Agriculture Department said Thursday follow-up tests confirmed the presence of the H1N1 virus, more commonly known as swine flu, in six samples taken as a part of a university research project at the Minnesota State Fair between Aug. 26 and Sept. 1.

The tests confirm the first cases of pigs contracting swine flu in the United States.

Officials say the pigs showed no signs of sickness and believe they contracted the virus from some of the nearly 1.8 million people who visited the fair.

The USDA has stressed that swine flu can't be contracted by eating pork products.

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