Secretary for Social Affairs and Culture Ao Ieong U urged non-essential businesses to close and called on residents to stay at home. Testing would be conducted from noon Sunday to noon June 21, Au said at a briefing in the city.

Authorities are sill investigating the source of the infections after uncovering some of the cases during the lockdown of a building where residents were tested, city health officials said at Sunday’s briefing. Four of the 12 people displayed Covid symptoms, they said.

The mass testing comes after the city last week eased quarantine requirements for arrivals from Hong Kong, Taiwan and other places. Authorities cut the isolation period to 10 days from 14, plus seven days of self monitoring.

The number of visitors to Macau plunged 24% in April from a year earlier after a 30% decline in March. Revenue for the city’s key casino industry dropped 68% in May to 3.34 billion patacas ($413 million) as China tightened travel restrictions during a record Covid outbreak.

On Saturday, Macau officials announced the city would entered an “immediate state of Covid-19 prevention” from Sunday after a preliminary positive case was detected in the community.

Macau is facing significant risk of Covid-19 transmission and outbreak in the community, the government said at midnight on Sunday. The territory’s chief executive has invoked relevant regulations to order the city into a preventive state from 1 a.m. local time, it added.