Bird flu has been found at two sites in Afghanistan and there's a high risk that tests could prove it to be the deadly H5N1 strain, a U.N. agency said Monday.

The U.N. Food and Agriculture Organization said five swab samples from backyard poultry farms in Kabul and the eastern city of Jalalabad tested positive on Monday for H5, and that tests were under way to discern the subtype.

"There's a high risk that the virus detected is H5N1, but other possibilities remain at this time," an FAO statement issued in Kabul said.