Ka Sing House at Ka Lung Court on Tin Wan Praya Road in Aberdeen was among the buildings placed on overnight lockdown.
A woman, 67, who visited the Little Boss pet shop in Causeway Bay on January 8 and has since been confirmed with the infection, lives in Ka Sing House.
Her husband, 73, is a preliminary-positive case.
Mei Foo Sun Chuen Phase 3 has also been sealed off.
A kindergarten teacher, 26, who tested preliminary positive, lives there. The authorities were still tracing the source of infection.
Residents of Monterey Cove Tower 1 in Caribbean Coast Phase 1 in Tung Chung were also ordered to be tested after a student, 16, tested preliminary positive.
He’s a classmate of an earlier confirmed case studying at the Delia Memorial School in Mei Foo.
Residents of the three buildings must stay put until their test results are out.
The authorities said they aim to complete the operations by 6:30am or 7am on Wednesday.
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Last updated: 2022-01-18 HKT 20:53