A second overnight testing operation at Block 2 of Hoi Tak Gardens on Wing Fat Lane was not concluded as of 7.30am.
Officials imposed the lockdowns on Thursday evening after a nurse and a nursing student who live in the buildings tested preliminary positive for the coronavirus.
Health officials said those who have recently been to the buildings must also be tested for Covid.
Officials said one of the infected nurses, 21, works part-time in local clinics, and is a nursing student at Baptist University’s School of Continuing Education.
Another nurse, 22, who works at the same clinics, also tested preliminary positive, though they worked different shifts.