The government on Tuesday detected 49 preliminary positive Covid-19 cases after locking down a building in Ma On Shan for testing.
Around 1,200 residents of Chung Wo House in Chung On Estate were tested.
Four test results were indeterminate.
Residents were allowed to leave their homes after 10:30am on Tuesday.
The lockdown, which began on Monday afternoon, was prompted by the discovery of sewage samples that tested positive for the coronavirus from the building.