The Agriculture, Fisheries and Conservation Department said the animal was tested after “abnormal” deaths of wild pigs were reported in Siu Sai Wan recently.
A spokesman said officials hadn’t discovered suspicious deaths in other areas so far and they will keep monitoring the situation.
He also said there are no pig farms on Hong Kong Island, and that the city’s pig farms have not been affected.
But authorities have reminded operators of local pig farms to step up measures to prevent wild pigs from entering.
African swine fever only affects pigs and does not infect humans.