Over 4.2 million people had been sampled for nucleic acid testing by 3:30 p.m. on Tuesday in east China's Qingdao, after it began a city-wide testing campaign on Monday.

Over 1.94 million of the collected samples have been tested so far and, with the exception of the confirmed and asymptomatic cases already reported, no new positive samples have been detected, the information office of the municipal government told a press conference on Tuesday.

Work including medical treatment, epidemiological investigations, and nucleic acid testing has been carried out in an orderly manner in Qingdao, said Chen Wansheng, an official with the municipal government.

Qingdao has reported six new confirmed cases and six new asymptomatic cases of COVID-19 since the virus re-emerged in the city over the weekend, the municipal health commission said.

The city has vowed to complete nucleic acid testing across five districts within three days starting from Monday, and testing will cover the whole city in five days.

More than 10,000 medical personnel have been deployed to conduct sampling and testing.