Health authorities say they found two preliminary positive cases after an overnight lockdown at numbers 21 to 35 Hung Kwong Street in To Kwa Wan, where they tested about 190 people.
No new Covid-19 cases were found during an overnight lockdown at Wai Chun House on Un Chau Street in Sham Shui Po.
About 40 people were tested in the Sham Shui Po operation.
People with proof that they had been tested were allowed to leave their buildings from 7 and 8 am on Wednesday morning.