People wearing protective masks wait in line outside a testing center for the government's Universal Community Testing Programme in Hong Kong on Sept 1, 2020. (PHOTO/BLOOMBERG)

HONG KONG - More than 1 million people have registered for the Hong Kong government’s mass testing program as the city reported seven new COVID-19 cases on Saturday.

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All seven cases were locally transmitted and three of them could not be traced, said health officials at a briefing in the afternoon.

Two of the untraced cases were identified in the city's Universal Community Testing Programme that started on Sept 1. They involved a 60-year-old man and a Filipino maid

Two of the untraced cases were identified in the city's Universal Community Testing Programme that started on Sept 1. They involved a 60-year-old man and a Filipino maid.

The city's infection tally stood at 4, 857.

As of 8 pm Saturday, some 1,058,000 residents have signed up for the free testing and some 847,000 have been tested, according to a government press release on Saturday.

In a Facebook post issued on Saturday morning, Secretary for the Civil Service Patrick Nip Tak-kuen thanked participants for helping to identify asymptomatic COVID-19 patients. He also thanked medical professionals who supported the program.

Hong Kong Secretary for Home Affairs Caspar Tsui (1st right) visits a special specimen collection center at Mui Wo Recreation Centre to inspect its operation on the first day, Sept 5, 2020. (PHOTO/HKSAR GOVERNMENT)

Hong Kong will extend the program at most testing centers by four days to Sept 11.

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On Saturday, the government also opened six special specimen collection centers in the Islands District for taking samples from residents there.

Inspecting one of the special centers in Mui Wo on Saturday, Secretary for Home Affairs Caspar Tsui called on residents to participate in the program to help identify early asymptomatic COVID-19 patients.

"Although the confirmed cases of COVID-19 have been gradually reduced recently, there are still silent transmission chains in the community," Tsui said.