Several ducks rest on the lawn in front of the Capitol Hill in Washington, the United Satates, September 2, 2006. -Xinhua/AFP

US Agriculture and Interior Departments said on Saturday that a low-risk strain of bird flu had been found in wild ducks in the state of Pennsylvania.

The mallards, sampled on Aug. 28 in Crawford County in northwestern Pennsylvania, tested positive for a low-grade strain of H5N1 bird flu.

The departments said in a statement, "Testing has ruled out the possibility of this being the highly pathogenic H5N1 strain that has spread through birds in Asia, Europe and Africa."

A second round of tests is being done at the National Veterinary Services Laboratories in Ames, Iowa, to confirm if the virus is the low-pathogenic H5N1 bird flu.

The ducks were sampled as part of the U.S. government's efforts to test as many as 100,000 wild birds in addition to more than 50,000 environmental tests throughout the country.

The low-pathogenic strain of H5N1 has been found many times in North American wild birds, but poses no threat to people.