Four preliminarily positive cases have been identified after mandatory tests in Sham Shui Po.
That came as the SAR reported 77 new confirmed cases yesterday, with more than half in coronavirus hot spot Yau Tsim Mong.
Residents from eight more buildings were also issued compulsory test orders, including four from designated areas in Yau Ma Tei-Jordan and Sham Shui Po - 511 Canton Road, 571-573 Canton Road, 27-31 Ning Po Street and 223 Yu Chau Street. Each had one infected unit.
The other four buildings are 7 Waterloo Road in Yau Ma Tei, Man Yiu Building in Jordan, Sheung Hong House in Ngau Tau Kok Upper Estate and block N of Kornhill in Tai Koo. They each had infections in two flats.
Apart from Kornhill where the infections involved adjoining units, the affected households in the three other buildings are on different floors facing different directions.
Chuang Shuk-kwan, head of the Centre for Health Protection's communicable disease branch, said all 77 new cases were local infections, with 37 from unknown sources.
That took the SAR's case tally to 9,798, with 166 deaths and more than 60 preliminarily positive patients.
Chuang said of 41 confirmed cases from Yau Tsim Mong, 20 were from the designated area bounded by Nathan and Jordan roads and Kansu and Ferry streets. There, residents must be tested upon one infection in a building.
Around 10 preliminarily positive patients also come from the area.
None of the cases came from within the designated area, where thousands of residents in 70 buildings were on Tuesday ordered to get tested regardless of whether their buildings, had seen patients.
Chuang said authorities do not know the ratio of tested residents in Yau Tsim Mong as most buildings there are private and many have subdivided units.
"The Home Affairs Department will send people to these blocks and knock on doors to ask residents to take the tests," she said. Some 18,000 residents from the designated area were tested from Saturday to Tuesday.
On the Sham Shui Po designated area bounded by Yen Chow and Maple streets and Tai Po and Lai Chi Kok roads, authorities on Tuesday issued compulsory test notices to six buildings, each of which had seen one case in the past 14 days.
Four preliminarily positive cases from Sham Shui Po were picked up in tests at mobile specimen collection centers.
Meanwhile, a North District Hospital nurse working in an isolation ward for Covid-19 patients tested preliminarily positive after a doctor tested positive.
Hospital Authority executive Linda Yu Wai-ling said that on January 5 the nurse took care of a 60-year-old male patient, whose condition took a turn for the worse that day, prompting medics to transfer him to the intensive care unit after a doctor connected him to breathing aids. The doctor tested positive Tuesday.
Yu said the nurse's residential building was not on the mandatory test list but she had worn full protective gear at work and the source of infection is being traced.
Her colleagues will be tested, while five who had meals with her went into quarantine.