Authorities have ordered all 3,000 pigs at a farm in northern Hong Kong culled after African swine fever appeared to be spreading at the facility.

Six samples taken from one shed on the premises at Wong Nai Tun in Yuen Long returned traces of the disease on February 4, triggering the culling of 240 pigs, and two additional samples from another shed came back positive on Saturday, prompting the killing of 590 more pigs, indicating it was spreading, the Agriculture, Fisheries and Conservation Department said on Tuesday.

The disease had never previously been detected in locally raised pigs.

After consulting international experts, the department decided to order the culling of the remaining 3,000 pigs.

“The department will cull the remaining 3,000 pigs in an orderly manner as the ground situation allows and as soon as possible,” a spokesman said. “The owner will be compensated according to the established mechanism.”

The disease is harmless to humans and not considered a threat to food safety but it spreads fast among swine populations and often proves deadly to the animals.

The spokesman said samples taken from three other pig farms within a 3km radius came back negative for swine fever.

After a major outbreak of the disease in mainland China in 2019 that resulted in more than 100 million pigs being either culled or dying, Hong Kong implemented stringent biosecurity measures, including cleaning and disinfecting vehicles going to the main Sheung Shui slaughterhouse.

Hui Wai-kin, head of the Pork Traders General Association, said swine from the city’s 38 licensed pig farms supplied about 22 per cent of local market demand and the culling would not have any impact as long as supplies from the mainland remained normal.

Hong Kong first detected the disease in pigs imported from the mainland in May 2019 that led to the culling of 6,000 pigs at the slaughterhouse.