WASHINGTON (Reuters) - Six pigs shown at the Minnesota State Fair last month have been confirmed as having had the pandemic H1N1 flu virus, the U.S. Agriculture Department said on Thursday.

　　The USDA said it is running confirmatory tests on samples from another six pigs that tested positive for the virus during preliminary tests. Some of those samples were collected at the South Dakota State Fair, the USDA said.

　　"People cannot get this flu from eating pork or pork products," the USDA said in a memo about the results.

　　The USDA found the virus in the first U.S. hog on October 19 -- one of the six positives from the Minnesota State Fair.

　　The virus, which infected as many as 5.7 million Americans between April and July, is commonly called swine flu. ID:nN29365484

　　The swine samples were taken as part of a research project that documents flu viruses in settings where people and hogs interact. ID:nN19386595

　　The project, funded by the U.S. Centers for Disease Control and Prevention, tested 57 samples from pigs at the Minnesota fair and 45 samples from the South Dakota fair.

　　There are no plans to conduct further tests on the samples that were negative for the flu, the USDA said.

　　The USDA said hog producers need to guard against the spread of the flu in hogs from people who are sick with the virus. Flu viruses, which are airborne, can pass back and forth between people and pigs.

　　The new strain of H1N1 virus, which has genetics from humans, birds and swine, likely circulated undetected in pigs for at least a decade before jumping to humans, according to an expert at the University of Arizona.

　　The USDA, which is working with manufacturers to speed the development of an H1N1 vaccine for hogs, said it plans to post all future suspected cases of the virus in hogs at www.usda.gov/H1N1flu 

　　The virus has been reported in hogs in Canada, and turkeys in Canada and Chile.