“Any social gatherings may lead to [a] rebound if we are not careful enough to maintain a certain extent of social distancing, hygiene and masks,” she said.

Chuang revealed that an outbreak at an industrial building in Tai Wai was growing, with one more case identified, bringing the number of infections in the cluster to 10.

The latest case was a 50-year-old cleaner who worked on all floors of the Transport City Building.

“She’s asymptomatic so I think there’s [danger] because we don’t know when she got the disease, but according to our existing protocol, the risk of her transmitting the disease to other persons since September 5 [her last day at work] is not high,” Chuang said.

The other three new cases were imported, involving arrivals from Ukraine and the Philippines.

Of the two patients found through the citywide screening programme, one was a close family contact of previously confirmed cases, and the other a symptomless housewife in Tuen Mun who mostly went to markets and malls in the district, Chuang said.

Eighteen new infections have now been identified through the programme.

The cases in the Transport City Building cluster, including security guards and tenants, were uncovered through contact tracing and the mass testing scheme.

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Chuang said 25 close contacts linked to the cluster had been identified and would be sent to quarantine, while some 400 test bottles had been distributed to workers at the 10-storey building.

Separately, around 2,000 inmates and staff at immigration detention centres and prisons had tested negative for the coronavirus so far. Officials had pledged to test more than 7,000 inmates after two men were confirmed as infected on Sunday.

At the Metropark Hotel in Mong Kok, where mass testing was carried out after four Covid-19 cases were recently recorded, most deep-throat saliva samples returned negative results.

Chuang said health authorities had tried to identify common activities among the infected hotel guests but had not yet found any.

The city, meanwhile, also edged closer to 100 Covid-19 deaths on Tuesday, as a 90-year-old resident at the Salvation Army Lung Hang Residence for Senior Citizens in Tai Wai died, taking the number of fatalities to 99. The institution has recorded 15 infections in total.

Earlier on Tuesday, the government said that from Friday, up to four people would be allowed per table in restaurants, as well as to meet in public.

A number of closed premises would be allowed to reopen, including museums, mahjong parlours, ice-skating rinks, and most indoor and outdoor sport facilities, but not swimming pools. Theme parks and exhibition venues could reopen next week if the health situation was kept under control.

The administration also revealed it was in discussions with about 11 countries, including Japan, Thailand, Germany, France and Switzerland, on forming travel bubbles.