Residents of the Port Centre were required to stay in their flats and undergo compulsory testing, with the whole operation expected to be wrapped up by 7:30 am on Friday.
The “restriction-testing declaration” does not include the shopping arcade.
“As a preliminary positive case with an unknown source was detected and the preliminary test result involved a mutant strain, the risk of infection in the relevant area is assessed to be likely higher,” a government spokesman said.
The Centre for Health Protection said the suspected case is a woman, 41, who worked as a part-time cleaner at Yau Ma Tei’s Bridal Tea House – a quarantine hotel.
Her last working day was Thursday and she has no recent travel history.
“She has been asymptomatic and was tested preliminarily positive via the regular testing for hotel staff members on June 30. Her specimen carried the L452R mutant strain,” the centre said in a statement, adding that she has not been vaccinated against Covid.
Health officials said she had also worked part-time providing cleaning services at Bluejay Residences in Ap Lei Chau and House 2, 12A South Bay Road in Repulse Bay, where she last went to work on June 27 and 29.
The woman’s workplaces and the places she had visited during the incubation and infectious period will be included in a compulsory testing notice, officials said.