All the cases were reported in Kashgar prefecture after a 17-year-old girl from Shufu county was confirmed as an asymptomatic carrier of the virus on Saturday during routine nucleic acid testing, reports Xinhua news agency.

The cases were all found related to a factory in Shufu where the parents of the girl work, Gu Yingsu, deputy director of the regional health commission, told reporters on Sunday.

She has been placed under quarantine for medical observation at a designated hospital in Kashgar, according to the health commission.

An epidemiological investigation that started on Saturday has combed all the close contacts of the new cases and those at risks, and health quarantine measures have been in place among them, the official added.

Kashgar has taken samples from over 2.83 million residents since Saturday, with test results obtained for 334,800 people.

The prefecture vowed to provide tests to about 4.75 million people in total including 245,000 in Shufu.

Earlier this month, the city of Qingdao tested its entire population of nine million people, the BBC reported.

In May, China tested the 11 million-strong population of Wuhan, the city where the novel coronavirus was first identified last December.