Authorities locked down another building at the Kwai Chung Estate at 10.30 pm on Saturday evening due to multiple cases in the surrounding area.
Residents of Chin Kwai House are required to be tested before 2.30 am on Sunday, regardless of their vaccination status, and will not be allowed to leave their homes until the results are mostly ascertained.
A government spokesperson says the operation is expected to finish at around noon on Sunday.