Hong Kong culled 4,500 birds on Tuesday after the deadly H7N9 bird flu virus was discovered in a chicken at a local market.
Health officials in white hazmat suits and masks dumped the chickens into green plastic bins at a wholesale poultry market in central Hong Kong.
The bins were then pumped with carbon dioxide to kill the birds.
Hong Kong is particularly alert to the spread of viruses after an outbreak of Severe Acute Respiratory Syndrome swept through the city in 2003, killing 299 people and infecting around 1,800.
Bird flu scares in the past two years have seen mass culls of up 20,000 birds in Hong Kong. A spokeswoman for the Agriculture, Fisheries and Conservation Department said the latest cull included chickens and pigeons.
Trade of live poultry has also been suspended after authorities said Saturday the avian flu virus was found in a fecal sample collected from a chicken at a market in the Tuen Mun, a neighborhood in the west of Hong Kong.
The city's health minister Ko Wing-man said the city was staying "stringent" against infectious diseases when he announced the cull late Monday.
H7N9 is a particular worry for authorities as it does not kill infected chickens or cause them to develop symptoms, which allows it to spread undetected until contact is made with humans.
The majority of human cases of H7N9 infection have been associated with direct or indirect contact with infected live or dead poultry, according to the World Health Organization.
Human infections from the H7N9 strain were first reported in China in 2013.
The virus can cause serious respiratory illness and has led to deaths.