The 54-year-old woman, who works for Cathay Pacific, tested positive for coronavirus in Australia on Thursday. She had tested negative in Hong Kong the day before departure.
The patient did not show any symptoms. She received two doses of the BioNTech vaccine earlier this year.
Health authorities have asked people who have stayed in Block 2 of Seaview Crescent in Tung Chung, where the patient lived, to get tested.
The Centre for Health Protection did not report any new Covid-19 cases in Hong Kong on Sunday.