Around 290 residents at Tsim Sha Tsui Mansion on Nathan Road, Tsim Sha Tsui faced an ambush-style lockdown at 8.30pm tonight.
Residents are required to stay at their premises and to undergo compulsory testing.
They are subject to undergo compulsory testing before 2am and the government expects to finish the exercise at about 7am tomorrow.
The mansion faces the lockdown as there is a confirmed case recorded recently.
Tsim Sha Tsui Mansion received a compulsory testing notice in mid-February, in which 60 were fined for breaching the testing order.
Authorities reported a new Covid
-19 case of unknown sources this afternoon, a 41-year-old housewife who lived in a guesthouse at Tsim Sha Tsui Mansion. She developed symptoms on March 4 and handed in a testing sample on the following day.