(To watch the full press briefing with sign language interpretation, click here.)

The Centre for Health Protection today said it is investigating 109 additional COVID-19 cases, of which 11 are imported and 98 are locally infected.

Among the local cases, 69 are related to Kwai Chung Estate, 24 are linked to other cases, while the sources of infection for the remaining five cases remain unknown.

At a press briefing this afternoon, the centre's Communicable Disease Branch Head Dr Chuang Shuk-kwan noted that there are so far about 210 positive and preliminary positive cases linked to Kwai Chung Estate.

She also reported that both the Delta and Omicron mutant strains have been detected in the sewage samples taken in Wong Tai Sin, reflecting that there may be silent transmission in the district.

Dr Chuang said: "For the Delta cases, we found two confirmed COVID-19 cases with the suspected Delta variant and they live in the same building. There is also a preliminary positive case in that building. They all live in Flat E on different floors of that block.

"So we are doing a multidisciplinary investigation and a site visit there to see what happens.

"In the three cases, one preliminary positive case who stayed in Flat E of the building, we just noted that he kept a hamster that he bought recently in a shop, but we are still asking for the details."

She appealed to residents and those who work in Wong Tai Sin to undergo voluntary testing as soon as possible.

In an update issued this evening, the centre said experts preliminarily considered that upward transmission of the virus via pipes is involved in the Wong Tai Sin building.

It will issue quarantine orders to asymptomatic residents of unit E on all floors of Block 1, Tropicana Gardens who stayed there during the incubation period of the relevant cases and transfer them to a quarantine facility. Symptomatic residents will be sent to hospital for treatment.

Separately, the centre will issue quarantine orders to residents of units 321 and 421 at Fu Keung House, Tai Wo Hau Estate due to the detection of another preliminary positive case involving a resident at unit 323.

It noted that a resident in unit 423 tested positive for COVID-19 earlier and experts preliminarily opined that downward transmission of the virus via pipes is involved.

As the pipes of units 323 and 423 are connected to those of the adjacent units, the centre decided to place residents of units 321 and 421 under quarantine.

Meanwhile, the Hospital Authority announced that a patient who visited Prince of Wales Hospital's psychiatric specialist outpatient clinic on January 18 tested positive for COVID-19.

In view of the case, 31 clinic staff members were arranged to undergo testing. One nurse preliminarily tested positive for the virus.

As the nurse wore appropriate personal protective equipment at work, none of the patients or staff members were classified as close contacts.

The Government tonight made restriction-testing declarations to cover Ha Kwai House of Kwai Chung Estate, Hing Fung Building in Sham Shui Po and Fu Tak House of Tai Wo Hau Estate, requiring people in the restricted areas to undergo compulsory testing.

In view of the cases which tested preliminary positive and those confirmed positive, as well as the sewage samples collected in Tai Wo Hau which also tested positive for the virus, 43 places are covered in a compulsory testing notice.

Meanwhile, in view of the confirmed cases found and some sewage samples which tested positive in Tai Wo Hau Estate and Wong Tai Sin, the Government calls on residents and those working in relevant areas who are exposed to infection risks to undergo testing.

The Government will set up additional service points tomorrow to enable residents and those working in relevant areas to undergo testing.

For information and health advice on COVID-19, visit the Government's dedicated webpage.