Dr Chuang Shuk-kwan, head of the communicable disease branch of the Centre for Health Protection, noted the port was a huge site, with thousands of workers operating across nine terminals on the 279-hectare site.

“We are arranging for all of the several thousand workers at the terminals to take a virus test. [Sampling] bottles will be given to them,” she said, adding that her team had asked the operators to carry out deep cleaning in places such as restrooms.

“The infected workers did not concentrate at a particular terminal. Some worked at Terminals 1 and 4. Some of them had meals in the same common room, and some used the same changing room. They were rather scattered.”

Coronavirus: China eases travel restrictions for visitors from Europe

Ken Lai Ma-kin, from the Union of Hong Kong Dockers, said hygiene at the terminals had been improved by the operators since a large strike in 2013, when workers demanded a pay rise and better working conditions.

He said many workers infected with Covid-19 at the terminals were part of the engineering unit at Terminal 6, and might have caught the coronavirus while eating together.

He noted that the workers had been more cautious about hygiene practices with the ongoing pandemic, but some based outdoors managing the cargo might not wear masks all the time.

Hongkong International Terminals (HIT), one of the major operators of the port, said seven of the cases worked at its terminals. Two of the seven had been discharged from hospital.

Modern Terminals, another operator, said a total of five workers under its two contractors providing internal haulage and stevedoring services had also tested positive for the virus.

Both operators said disinfection was done in areas of the terminals, and operations remained normal.

They also said they had been given test kits from the Department of Health. HIT said it had collected 3,000 kits on Tuesday, and would prioritise testing close contacts of the confirmed cases. It also said it would get extra test kits from the government to broaden the reach.

Modern Terminals said its kits would be given to outdoor workers, who would be tested on a voluntary basis.

Other new cases on Wednesday included an Indonesian domestic worker, who had stayed with five other helpers from July 25 to 31 in a dormitory at Haven Court, in Causeway Bay.

Chuang said the patient had gone on to live from August 1 to 10 in Sai Kung with her new employer. Eleven people in the family have been deemed close contacts.

Chuang admitted difficulties in tracing people who had used another dormitory in Cheung Hing Mansion in Mong Kok, after a helper who had also stayed there was confirmed as infected a day earlier.

She said police were helping after the landlord proved uncooperative.

“If an employer has recently hired an Indonesian helper, better ask if they had stayed … [on] the 9th floor of Cheung Hing Mansion. If so, a virus test might need to be arranged,” Chuang said.

Hong Kong has so far recorded 4,243 confirmed cases and 63 related deaths.

The latest infections marked the 10th straight day of the city confirming a double-digit increase to its total, after a 12-day run of triple-digit surges.

While Wednesday’s caseload almost doubled the tally of 33 recorded the day before – the lowest daily count in nearly a month – Chuang cautioned against reading too much into it.

“Every day we have seen fluctuation, it may have something to do with [the amount of] sample returning and testing,” she said, “but there is some decrease in the overall trend.”

Dr Joseph Tsang Kay-yan, a specialist in infectious diseases, said there were lots of variables affecting the amount of cases recorded daily.

Covid-19 social-distancing rules take heavy toll on Hong Kong’s restaurants

“With cluster outbreaks going on, there is a possibility that there would be delay [in reporting time] of those close contacts, as everyone’s incubation period of the virus is different,” Tsang said.

He also said bottlenecks in some procedures, such as contact tracing and turnaround time of virus test results prepared by the public sector, could mean infected patients would remain in the community longer, putting more people at risk.

Two nurses were also among the more than 30 preliminary positive cases reported on Wednesday. The first one, from the internal medicine department of the Pamela Youde Nethersole Eastern Hospital in Chai Wan, fell ill on Tuesday after working an overnight shift.

While she did not look after confirmed Covid-19 patients, there was one who lived in her building, and 13 colleagues who shared meals with her will now undergo quarantine.

The second nurse works in United Christian Hospital’s psychiatry department. Five colleagues who dined with her are regarded as close contacts, while some 20 patients in her ward, as well as all the environmental samples taken, had tested negative for the virus.

All four patients who died on Wednesday were elderly, aged from 78 to 93. Two were residents of care homes, including a 79-year-old man who was a resident of King Fok nursing home in Sham Shui Po, and a 91-year-old woman who previously stayed in the Salvation Army Lung Hang Residence for Senior Citizens in Tai Wai.

The other two fatalities were a 78-year-old man and a 93-year-old woman. Both had long-term illnesses.