“We really appeal to employers if they have employees caught in this operation that, I hope, they will treat this in a more open and understanding manner so they won’t deduct people’s salary and things like that.

“The most important aim is really to identify or detect cases within the building, and secondly we want to stop the transmission chain from going further, therefore this is for the common good.”

Chan said evacuating everyone from the affected block was not necessary because the outbreak was related to environmental contamination, not building structural issues.

The government first ordered a lockdown that lasted for longer than a day in January last year, in a 48-hour operation involving about 70 blocks in Jordan.

Asked why the Kwai Chung lockdown would last five days, Centre for Health Protection (CHP) controller Edwin Tsui Lok-kin said it was necessary to detect infected residents while the virus was incubating.

Residents would be subject to daily screening over the five days with the disabled and elderly tested at home.

The lockdown was carried out under the Prevention and Control of Disease Regulation, through which overnight lockdowns are currently conducted. Failure to comply with the order will result in a HK$5,000 fine. Further violations will incur a maximum penalty of six months’ jail and a HK$25,000 fine.

Superspreader fears spark 3 days of Covid-19 testing at Hong Kong block

Authorities confirmed 24 new coronavirus cases citywide on Friday, 18 of which were locally transmitted including two untraceable infections. The rest were imported. The additions brought the tally of confirmed infections to 13,120, with 213 related deaths.

About 20 preliminary-positive cases were reported, including about 10 linked to Yat Kwai House.

An unvaccinated man believed to have contracted the coronavirus from his wife had visited Yat Kwai House on January 13 to collect items from refuse stations for recycling. The wife, who had recently returned to the city from Pakistan, tested positive for the Omicron variant days after her three-week hotel quarantine ended, leading experts to believe she had caught Covid-19 from a fellow guest.

Health officials said they believed the man infected a 64-year-old female cleaner, who spread the virus to residents from 13 households across 12 floors, as well as building staff.

“The cleaner came into contact with the most people. We feel this is the most likely reason so many people were infected,” Tsui said.

The woman, who had received two doses of the Sinovac vaccine, also lives on the estate in Ying Kwai House, where one preliminary case was reported on Friday.

The Housing Department is in charge of the lockdown and will deliver three meals a day to residents. A medical post has also been set up for residents’ inquiries.

Elsewhere in the city, a cluster linked to pet shops grew to eight people, with the latest infections involving two customers of the Little Boss store in Causeway Bay and another at its Mong Kong branch, as well as a family member.

The untraceable confirmed cases are two men, aged 24 and 37, who live, respectively, in Cheung Yan House at Cheung Sha Wan Estate and the New Haven development in Tsuen Wan. Another untraceable preliminary infection involves a 40-year-old construction worker who lives on Nam Cheong Street in Sham Shui Po.

A diner at the Dragon Place restaurant in Aberdeen was also confirmed as infected. Authorities noted that while he was seated far from a previously infected customer they both went to the toilet, where officials suspect transmission had occurred.

Government pandemic adviser Professor David Hui Shu-cheong earlier said he believed the transmissions at Yat Kwai House had occurred via environmental contamination in communal places, such as lobbies, postboxes and refuse rooms.

Similar transmissions and lockdowns could take place elsewhere as the city’s Omicron outbreak grew, he warned.

The Home Affairs Department has given out Covid-19 rapid self-testing kits to 3,460 households in four public housing blocks close to Yat Kwai House.

Leung Chi-sing, a district councillor for the Kwai Hing constituency, said most of the residents in Yat Kwai House were worried about the outbreak and concerned that security guards had allowed a stranger to enter.

“Residents should avoid interacting with each other,” he said. “Security guards should also reject the entry of non-residents. We hope the Housing Department can step up security in the estate.”

Some residents rushed to buy food and daily necessities on Friday morning, he said, while some employers had advised staff not to go to work.

Construction worker Ng Wai-chung, 48, said the lockdown would leave him with an unacceptable financial burden.

“My boss might fire me if I am gone for five days. Will the government make it up for me?” said Ng, who lives with his wife, their son and his mother.

As the breadwinner, he was worried he could lose at least HK$10,000 during the lockdown.

Iris Chang Yee-man, president of the Practising Pharmacists Association, estimated about 10 to 20 per cent of estate residents had chronic illnesses and needed medication.

“We understand there may be a number of residents who are unable to secure medicine in the coming days because of the sudden home quarantine order,” Chang said.

She urged those with medical needs to register with the pharmacist-led online platform Medsgo.org to get adequate supplies of their medication delivered to their homes during quarantine.

Additional reporting by Kathleen Magramo, Nadia Lam and Tiffany Liang