The latest bird flu outbreak on a Hong Kong chicken farm was caused by the highly virulent H5N1 strain of the avian influenza virus, the Hong Kong Special Administrative Region (HKSAR) government confirmed on Thursday.

The Agriculture, Fisheries and Conservation Department said test results confirmed the virus to be H5N1 on Thursday afternoon, two days after samples collected by the department tested positive for the H5 strain.

It was the first outbreak of H5 bird flu on a Hong Kong farm in about six years.

Health authorities declared the area within three kilometers of the affected farm an infected place on Tuesday and ordered the slaughtering of 90,000 domestic birds.

York Chow, secretary for food and health, said health authorities have been testing samples collected from other farms, including a second farm within the infected area.

"We have tested the chickens in the second farm, which turned out to be negative for H5. So far we have not found any positive samples from the other farms," he said.

"But we will do more samples in the coming weeks," he added.

The Agriculture, Fisheries and Conservation Department has also been reviewing and upgrading biosecurity measures put in place by local chicken farms.

The number of hens, cocks, chickens and fertilized eggs were consistent with records kept and updated on a regular basis by the department, it said.

(Xinhua News Agency December 12, 2008)