The Centre for Health Protection (CHP) today said it is looking into 21 additional COVID-19 cases, of which 13 are imported and eight are epidemiologically linked with imported cases.

Among the new cases, 20 involve mutant strains while the mutation test result of the remaining case is pending.

One of the linked cases involves a 48-year-old man who lives in Maple Gardens Phase III in North Point. He works at CITIC Securities Company in the district and last went to work on January 5. Three of his colleagues were infected with COVID-19 earlier.

The patient was classified as a close contact of one of the infected colleagues and was arranged to undergo quarantine at the Penny's Bay Quarantine Centre on January 8. He remains asymptomatic and tested positive yesterday.

The Government made a restriction-testing declaration for the building where the patient lives, requiring people within the restricted area to get tested by midnight.

Meanwhile, another restriction-testing declaration was made to cover Block 3, Po Tin Estate in Tuen Mun due to the detection of a preliminary positive case. People within the restricted area need to undergo compulsory testing by 1am tomorrow.

The case involves a 51-year-old woman who is a security guard at the Penny's Bay Quarantine Centre. She has to undergo frequent regular virus tests and last tested negative on January 8. But she developed a fever and tested preliminary positive yesterday.

The CHP is investigating the places the woman had visited during the incubation period and will carry out whole genome sequencing analysis to ascertain the infection source.

At a press briefing this afternoon, the CHP's Communicable Disease Branch Head Dr Chuang Shuk-kwan said it could not exclude the possibility of silent transmission chains in Tuen Mun.

Dr Chuang noted that there are quite a number of confirmed COVID-19 cases in the district, including a family linked to a pharmacy in the area as well as a preliminary positive case who lives in Tuen Mun.

She called on citizens to see a doctor or undergo a COVID-19 test as soon as possible if they feel unwell or have any symptoms. Family physicians are also urged to test patients, even those with mild symptoms.

To facilitate people living, staying or working in Tuen Mun to get tested, there will be 10 testing service points in the district in the coming few days, including several additional mobile specimen collection stations. The community testing centre at Siu Lun Community Hall will extend its operating hours to 10pm from today.

Meanwhile, in view of one import-related case and six preliminary positive cases, 31 specified premises are included in the compulsory testing notice. Three schools where an outbreak of upper respiratory tract infection or influenza-like illness occurred are also covered in the notice.

The Government will set up mobile specimen collection stations at various locations for people who are subject to compulsory testing.

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