La Rossa A (Block 7) of Coastal Skyline Phase 3 was cordoned off at 8pm and residents are required to undergo testing before 1am.
“As some cases tested positive who have lived in the building were detected recently, and the test results involved mutant strain, the risk of infection in the relevant area is assessed to be likely higher, so the Government decided to make a ‘restriction-testing declaration’ for the relevant area,” a government spokesman said.
Officials said they aimed to lift the lockdown at about 7am on Thursday.
The Centre for Health Protection earlier said a few Covid-19 patients had visited an outdoor area at the Coastal Skyline housing estate where around 30 people regularly played football and spent time.