Chief Executive of the Hong Kong Special Administrative Region (HKSAR) Carrie Lam on Tuesday urged locals to all take a COVID-19 test as the city's mass free screening program started with the help of medical experts from Chinese mainland.

Every Hong Kong resident will be eligible for one free coronavirus test as part of the voluntary Universal Community Testing Programme (UCTP). Official data shows that as of Monday evening, about 553,000 people have successfully registered.

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The mass testing would help reveal all asymptomatic cases as such patients consist a quarter of the new infections, Lam noted, hoping Hong Kongers see the program in a "fair and objective light."

The chief executive reassured that privacy will be protected as labs will not be given personal information about test takers.

Hong Kong has reported over 4,800 infections since the virus first hit the city in late January, with 88 deaths so far. About 75 percent of those infected were detected in a new outbreak that began in early July. 

Lam and some other principal officials of the government took their tests on Tuesday, the program's opening day.

(CGTN's Zhu Dan contributed to the story.)