Officials began slaughtering tens of thousands of chickens at a poultry farm in southern Japan on Friday, following a new outbreak of bird flu this week.
It was not yet clear whether the virus that killed 3,000 chickens at the farm in Hyuga, in Japan's southern Miyazaki prefecture (state), was the deadly H5N1 strain.
A state laboratory near Tokyo was analyzing a virus taken from the dead chickens, and results were expected over the next few days.
About 150 officials from the prefectural government began culling about 49,000 remaining chickens at the Hyuga farm and packing the dead birds in bags, said official Hisao Takase.
Later Friday, the prefectural government announced a plan to kill 50,000 more chickens at a next-door farm as a precaution, another Miyazaki official Mamoru Tsunekichi said.
In another Miyazaki town earlier this month, 4,000 chickens died from the H5N1 strain.
The H5N1 virus has ravaged poultry stocks in Asia since 2003 and has killed at least 163 people around the world, according to the World Health Organization.
One human H5N1 infection has been confirmed in Japan, but no reported human deaths.
Bird flu remains hard for humans to catch, but international experts fear it may mutate into a form that could spread easily among humans and potentially kill millions around the world.
Miyazaki, about 900 kilometers (560 miles) southwest of Tokyo, is Japan's main chicken-producing region.