WASHINGTON - A second round of tests on ducks in central Illinois confirmed the birds have a low-pathogenic form of avian influenza, the U.S. government said Tuesday.

The low-pathogenic H6N2 virus was found in five of the 11 samples collected from wild Green-winged Teals in Fulton County, Illinois, the U.S. Agriculture Department and the Department of Interior said in a joint statement. Early testing on September 29 indicated it might be the low-pathogenic strain of H5N1.

The low-pathogenic avian influenza virus commonly occurs in nature, but usually results in minor sickness or no noticeable disease for birds.

Low-pathogenic bird flu has been confirmed in the United States this year including in Michigan, Montana, Pennsylvania and Maryland.

In an effort to detect the high-pathogenic H5N1 strain that has killed 151 people overseas, USDA and the Department of the Interior are working with the states to collect between 75,000 and 100,000 wild bird samples in addition to more than 50,000 environmental tests throughout the United States.