Residents of buildings in Sham Shui Po, Jordan and Tin Shui Wai are required to remain at home overnight until they test negative for Covid-19.
The lockdowns were announced shortly after 7pm. In Sham Shui Po, 17 buildings on Ki Lung Street, Nam Cheong Street, Tai Nan Street and Pei Ho Street are affected.
The closure in Jordon, meanwhile, includes buildings on Cheong Lok Street, Chi Wo Street and Nathan Road.
Heng Lok House at Tin Shui Wai’s Tin Heng Estate has also been sealed off.
Testing is expected to continue into the night, with the aim of completing the operations by around 7 or 7:30 on Wednesday morning to allow residents to return to work.
The government called for understanding, saying the move is aimed at achieving “zero infections” in the community.
Officials have said such operations are not useless even if they don’t find a single coronavirus infection because they can help put residents’ minds at ease.
Chief Secretary Matthew Cheung on Monday warned that the authorities will be ramping up mandatory testing ahead of the Lunar New Year break to try to control the outbreak, to see if social gathering restrictions can be eased afterwards to allow businesses and schools to reopen.