After an outbreak of avian influenza (search) was discovered at a Delaware farm, state authorities have tested several nearby facilities but have not released the results.

Scientists will not release the results of a first round of tests until a second round is complete, said Anne Fitzgerald, a spokeswoman for the Delaware Department of Agriculture (search). It was not immediately clear when the results would be released.

The flu strain is different from the one that has spread to the human population in Asia, and experts say there is no threat to human health. Some Asian countries, however, have banned U.S. poultry imports following the outbreak in Delaware.

Delaware authorities on Saturday began testing chickens at 12 farms within a 2-mile radius of an infected farm in Kent County, where 12,000 chickens were destroyed Saturday. Fitzgerald said officials tested five farms Saturday and three Sunday, with officials planning to test four more.

The exact location of the infected farm hasn't been disclosed.

Japan, Malaysia, Singapore and South Korea banned U.S. poultry imports following the outbreak. Hong Kong (search) banned the import of live birds and poultry from Delaware only.

Avian influenza spreads easily among animals through nasal and eye secretions, as well as manure.

The strain found in Delaware, known as H7, has the potential to cause severe economic damage if it spreads to the commercial broiler industry, a linchpin of the region's agricultural economy.

A different form of bird flu has ravaged poultry farms across Asia, where more than 50 million chickens have been slaughtered to stem the disease's spread. At least 18 people have died in Asia from the H5N1 strain. Experts there say there's no sign the virus is changing into one that could spread widely among people.

The U.S. government has banned the import of birds from eight Southeast Asian countries.