Health officials in Hong Kong killed about 20,000 chickens Tuesday after the deadly H7N9 bird flu virus was found in poultry imported from the mainland.
Dressed in white protective coats and masks, the workers loaded up birds by the handful into black plastic bags, which were then filled with poison gas.
Hong Kong's secretary for food and health, Ko Wing-man, said late Monday the infected poultry was imported from the southern province of Guangdong.
"The Agriculture, Fisheries, and Conservation Department has confirmed that a sample taken from a chicken imported from the mainland [China] was tested positive for the H7N9 avian influenza virus," said Ko.
The Cheung Sha Wan market, where the virus was found, has been sterilized and will be closed for the next 21 days. Live chicken imports from the mainland have been suspended.
Authorities in eastern China have also announced a ban on live poultry sales, amid fears the virus might spread more easily during the Lunar New Year holiday season, when many people travel.
The World Health Organization says there is no evidence of sustained human-to-human infection of the H7N9 virus. It instead spreads bird-to-bird.
Chinese state media report 98 people have been infected with the H7N9 virus so far this year, and that 19 have died.
Two people have died in Hong Kong since December after becoming infected with H7N9 in the mainland.
A more common form of avian flu, H5N1, has killed more than 360 people worldwide in the past decade, including many in China.