A dead buzzard found on an outlying Hong Kong island tested positive for the deadly H5N1 strain of bird flu, the second such case in two weeks, the government said Friday. Test results confirmed the diagnosis of the common buzzard found Monday on Lantau island, the Agriculture, Fisheries and Conservation Department said in a statement. The government last week ordered its famed Mai Po bird sanctuary closed for three weeks as a precaution after a dead gray heron found nearby tested positive for bird flu. Hong Kong occasionally discovers wild birds infected with bird flu, but it hasn't had a major outbreak of the disease recently. Experts fear bird flu could mutate into a form easily transmissible among humans and spark a flu pandemic. Hong Kong aggressively monitors bird flu because the first documented cases of the disease in humans occurred in the territory. An outbreak of H5N1 in 1997 killed six people. That prompted the government to slaughter the entire poultry population of about 1.5 million birds.