Health authorities found 107 positive cases after three buildings were locked down overnight for Covid-19 testing.
Officials found 53 positive cases at Cheung Chi House of Cheung Wah Estate in Fanling, and 21 cases were indeterminate.
At Kwong Yan House of Kwong Fuk Estate in Tai Po, 40 people tested positive and 27 cases were indeterminate.
And there were 14 positive cases at Chung Shue House of Lei Muk Shue (II) Estate in Tsuen Wan.
In all, nearly 3,800 people were tested.
Meanwhile, several more buildings were placed under lockdown for testing after either the discovery of positive sewage samples or infections were reported there.
They are blocks 7 and 8 of Richland Gardens in Kowloon Bay; Block 6 of Dawning Views in Fanling; and Ching Yeung House of Cheung Ching Estate in Tsing Yi.
Officials hope to complete the operations at 1pm on Wednesday.