The Centre for Health Protection said the 71st case was a 68-year-old man who recently flew back to Hong Kong on a government-chartered flight from the quarantined Diamond Princess cruise ship in Japan.

The 72nd case is a 62-year-old man who lives in and works as a security guard at Choi Tin House, Hing Tin Estate in Lam Tin. He had not travelled outside Hong Kong recently. He attended a company dinner with 17 others at a restaurant in the Silvercord shopping centre in Tsim Sha Tsui on February 10.

The 73rd case is a 80-year-old woman who frequently visits Fook Wai Ching She Buddhist worship hall at the Maylun Apartments building on King’s Road in North Point. She last went there on February 8.

The 74th case is a 76-year-old woman who lives in Maylun Apartments and visited the worship hall every morning. She developed a fever on February 13.

Dr Chuang Shuk-kwan from the Centre for Health Protection said about 30 people had contacted the government to say they had visited the Buddhist hall recently, fearing they may be infected.

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Two others earlier confirmed to have the virus had also visited the hall.

As of Sunday, five worshippers said they felt unwell and had been sent to hospital. Ten other people have been placed under quarantine.

“We hope to carry out disinfection [of the hall] and take some environmental samples there as soon as possible,” Chuang said. “And the outbreak all points to the hall itself, potentially due to shared apparatus or having some contact inside.”

She said there was no need to evacuate the building yet. The four who contracted the virus lived in different locations and did not know each other, Chuang said, adding visitors may have shared food or recited Buddhist readings there for hours.

Health officials were initially unable to contact the master of the hall from Saturday night and had to obtain a court warrant on Sunday. They were later allowed in to inspect the hall and take samples there.

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A police source said the force had not yet received a request from the Department of Health to trace people who had visited the Buddhist hall, but was prepared to help if needed.

Meanwhile, 26 more police officers were listed as close contacts of the first infection case in the force, bringing the total number who need to be quarantined to 85. The infected 48-year-old policeman had attended a dinner gathering with 59 colleagues on February 18 while the latest group had all worked or dined with him two days earlier.

However, as of Sunday noon, only 28 officers had been placed under quarantine. Chuang said that was because of the large number of close contacts in the case, while on the same day the first group of passengers from the Diamond Princess cruise were sent into quarantine.

“Somehow, we’ve been caught off guard [with the amount of work],” Chuang conceded.

Tests for the coronavirus were also being done for a 35-year-old driver, who last returned from mainland China on February 7, according to health officials. Medical sources said a preliminary saliva test was positive.

Last week, the authorities broadened the scope of their surveillance, and collected deep throat saliva samples from anyone with fever or respiratory symptoms.

Two medical sources said the driver returned one day before the Hong Kong government closed the border, or would otherwise have faced a 14-day mandatory quarantine.

The driver went to Pok Oi Hospital, in Yuen Long, after developing symptoms on Friday, and was admitted to Tuen Mun Hospital on Saturday.

His first test for the virus was indeterminate, but a later one was positive.

Separately, a 33-year-old woman was discharged from hospital on Sunday, bringing the number of recovered patients to 12 in total. She was in the family who attended a hotpot gathering that led to multiple infection cases. The woman was admitted to Ruttonjee Hospital in Wan Chai on February 8.