Authorities in Macau instructed residents to conduct at least two days of COVID-19 tests after a person who traveled from the Chinese special administrative region to the neighboring city of Zhuhai was found to have been infected with the virus.
The move comes days after Macau started to unwind stringent anti-COVID-19 rules, including the resumption of travel to Zhuhai without quarantine from Aug. 3.
The Macau government said in a statement on Sunday that all of the city's 700,000 residents should take rapid antigen tests on Sunday and Monday and upload the results to a government website.
Thousands of residents living near Macau's border to Zhuhai and the Taipa district, which sits alongside the city's Las Vegas-style Cotai strip, must do official nucleic acid tests, the government said.
Authorities have also sealed up the infected person's apartment building and the supermarket where the person worked.
Macau reopened public services and entertainment facilities and allowed the resumption of in-restaurant dining on Aug. 2.
The former Portuguese colony has reported around 1,800 infections since mid-June when it was hit with its worst coronavirus outbreak that forced the closure of casinos and locked down most of the city.
More than 90% of Macau's residents are fully vaccinated against COVID-19, but authorities have closely followed China's zero-COVID mandate which seeks to curb all outbreaks at almost any cost, contrary to much of the rest of the world which is already adjusting to living with the virus.