The three men and one woman, who returned from the Philippines and Pakistan, were all fully vaccinated.
Separately, health authorities ordered residents at block three of Tung Chung’s Caribbean Coast phase one to get tested after a man who lives in the building tested positive for the virus when he arrived in Australia on Tuesday.
Health officials said the 55-year-old cargo flight crew member had tested negative the day before his departure and contact tracing was underway.
Meanwhile, the government announced that seven facilities will stop collecting people’s deep throat saliva samples for Covid testing from October 4 after reviewing the service and demand.
The facilities include the government headquarters in Admiralty, Shau Kei Wan chest clinic, Tai Wan Shan swimming pool in Hung Hom and Tai Po waterfront park.