They had sealed off the residential building at the Golden Lion Garden development at about 7pm on Thursday, after one resident tested preliminary positive for Covid-19.
The Centre for Health Protection says the case involves a 48-year-old man, who works as a cargo handler at the airport. His sample had come back preliminary positive on Wednesday. The fully-vaccinated man had no recent travel history and was asymptomatic.
If the case is classified as a local infection, it will be Hong Kong’s first local case in almost two months.
In addition to locking down the block overnight for testing, the man’s workplace – as well as the venues he visited during the incubation period – have also been included in a compulsory testing notice.
Separately, Hong Kong recorded eight imported Covid cases on Thursday.