(Bloomberg) -- Hong Kong is investigating a new cluster that may involve nine patients in a resurgence of infection that ends a 16-day streak of no local transmission.

Hong Kong Chief Executive Carrie Lam said at a briefing Tuesday that the new cluster indicates that the virus has probably spread both at a residential building and in the workplace, and its emergence will make authorities more cautious about easing social distancing restrictions.

Four infected people living in the same Sha Tin building as a couple earlier confirmed with the pathogen have been found, reported Radio Television Hong Kong late Monday. But it’s still unclear if they had any contact with the couple -- a 34-year-old woman, whose job is labeling imported packaged foods, and her 56-year-old husband -- said the report citing unidentified sources.

Health officials said there was no need at this stage to evacuate people from the building, according to the report.

The weekend cases ended Hong Kong’s 16-day streak of no new local transmissions even as the city started to relax some social distancing measures. The food labeling worker was linked to three cases on Monday, including two of her colleagues and a paramedic who brought the patient to hospital.

The emergence of hidden local transmission chains is a setback to government plans to ease measures further, including reopening schools and loosening border restrictions with mainland China. After months of social distancing, Hong Kong was on the verge of reverting to normal life. Instead, the Asian financial hub now faces a potential resurgence of cases as it’s unclear how many people the woman came into contact with before her infection was identified.

Marks & Spencer said earlier Monday in a Facebook post that it was informed by one of its logistics partners that a part-time employee had tested positive for Covid-19, the illness brought on by coronavirus. The company is disinfecting all its stores in Hong Kong.

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