The Centre for Health Protection today said it is investigating four additional COVID-19 cases, of which three are imported and one is a possible local case with an unknown source of infection.

The imported cases arrived from Indonesia and India and involve three women.

The possible local case is a 48-year-old woman with the N501Y mutant strain of the virus. She lives at Block R of Allway Gardens in Tsuen Wan.

As the N501Y mutant strain has a high transmissibility, the centre will transfer asymptomatic residents of all units on all floors of the building involving over 220 units to quarantine centres, while symptomatic residents will be sent to hospital for treatment.

They will undergo compulsory quarantine for 21 days.

The Government today made a restriction-testing declaration for the building which took effect from 7.30pm and aims to be finished by about 7am tomorrow. People in the area subject to compulsory testing will need to be tested by midnight.

Diploma of Secondary Education candidates in the restricted area who need to sit for the examination the following day should go to the temporary specimen collection stations there as soon as possible and submit relevant documents including admission forms for proof to undergo priority testing.

Meanwhile, according to the compulsory testing notice, any person who had been at the building for more than two hours from April 21 to May 4, even if they were not present in the restricted area when the declaration took effect, must undergo compulsory testing by May 6.

A total of 91 cases have been reported in the past 14 days, including 19 local cases of which 10 are from unknown sources.

Additionally, another compulsory testing notice will cover 12 premises relating to confirmed and preliminary positive cases, all of which involve the N501Y mutant strain, as well as 23 schools with outbreaks of upper respiratory tract infection and/or influenza-like illness. Relevant citizens are required to undergo compulsory testing.

The Government will add mobile specimen collection stations at D‧PARK in Tsuen Wan and Sai Kung Jockey Club Town Hall tomorrow, and extend the service period of the station at Fu Tung Estate in Tung Chung to May 7 to serve citizens subject to compulsory testing.

Foreign domestic helpers who have yet to receive testing may still make use of the service provided at community testing centres and mobile specimen collection stations in the coming few days.

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