It was not immediately clear whether Tuesday’s cases were local or imported. They included an 85-year-old woman and a 79-year-old man who lived in Kong Tai Care for the Aged Centre Limited.

A source said another person from the care home was showing signs of fever and had been sent to hospital for a check-up, amid fears of an outbreak at the centre.

Other positive cases included a 40-year-old man who worked at the information technology division in the head office of the Hospital Authority, located in a block in Kowloon Hospital. He lived in Wo Che Estate in Sha Tin.

Another resident from the same estate but a separate household, a 42-year-old man, also tested positive for the virus.

Amid the re-emergence of locally transmitted cases, four schools suspended classes on Tuesday, including two institutions where students were infected by Covid-19.

In a notice to parents, CCC Rotary Secondary School in Wong Tai Sin said it had been advised by the Education Bureau to suspend classes from Tuesday and thoroughly disinfect the campus, after a Form Three student was found to have contracted the virus.

It was not immediately clear whether that student was the 14-year-old revealed earlier as testing positive for the virus.

That came as a student at the Hong Kong Academy for Performing Arts, which has campuses in Wan Chai and Pok Fu Lam, also contracted the virus.

The academy said the student had not visited any of its sites from June 17, but all pupils and staff were told to immediately leave the campus as face-to-face activities had been suspended from Tuesday.

At Fung Kai Innovative School in Sheung Shui, classes were suspended after a teacher reported spending “a short time” in the company of an infected patient last Saturday. The school said the teacher would be tested.

G.T. Ellen Yeung College’s Mong Kok campus also suspended face-to-face lessons on Tuesday, after learning that the parent of a primary school pupil shared a meal with an infected patient more than a week ago.

The school said the parent had tested negative for the virus, and it was still under discussion whether the suspension would continue.

Cluster fears after two new local Covid-19 cases in Hong Kong

But classes went on as usual at Kwong Ming Ying Loi School in Yuen Long where a family member of a teacher got infected. The school said the employee had been placed under home quarantine, while students who had come in contact with him had been moved to other classrooms for lessons.

Classes continued at Stewards Pooi Kei Primary School in Sha Tin as well, where the father of a Primary One student returned preliminary positive results. But the school said the pupil did not attend classes on Tuesday.

Dr Leung Chi-chiu, chairman of the Medical Association’s advisory committee on communicable diseases, said there were risks of the emergence of a new cluster amid recent reports of several locally transmitted virus cases in the city.

He urged the government to speed up tracing the contacts of the patients to stamp out infection sources within the community.

“It is relatively obvious that it is about our loopholes [in handling inbound travellers]. They lead to a third wave of infections, which may already have happened,” he said on a radio programme.

“The current situation perhaps only reflects the infection problems in the previous one or two weeks due to diagnostic delays or incubation period-related issues.”

Hong Kong’s three-week streak of zero local infections ends, as authorities consider tightening rules on test exemptions

He said transit flight services resumed in June and some of the city’s quarantine exemption arrangements were more relaxed compared to other places, adding that the government should review and tighten its anti-pandemic policies such as quarantine arrangements.

For example, he said the government could find some hotels for quarantining those who entered Hong Kong.

“We have to be forward-looking in making these measures,” he said.

The public should cut back on activities involving close contact with non-family members, he said, while adding that masks should be worn for indoor activities.

Lam added that the steering committee meeting would also look into the city’s quarantine facilities.

“I very much hope that we can return Chun Yeung Estate to the residents waiting to move into their new homes. I think the new quarantine centre in Penny’s Bay can be used this month,” she said, referring to the facilities on Lantau Island.

Meanwhile, Professor Ignatius Yu Tak-sun, from Chinese University, said there was a possibility that the virus could spread through airborne transmission.

He said the particles people produce when they talk loudly, sing, cough, or sneeze, could stay in the air and be breathed in by others.