The city of Qingdao in eastern China has tested more than 3.07 million people for Covid-19 since the weekend, when 12 locally transmitted cases were reported, according to the city's information office.
No new cases have been identified by the citywide testing program from the more than 1.1 million samples already returned, the information office said in its statement on Tuesday.
Containing an outbreak: The 12 cases -- split evenly between symptomatic and asymptomatic cases -- were all linked to the Qingdao Chest Hospital, which had been treating imported infections. The cluster prompted a mass testing program of the city's 9 million residents, which began on Monday.
Some 130 testing stations have been set up in Shinan district, the city's center of political and business activity.
Authorities said the specific source of infection is still under investigation.
Read more about the situation in Qingdao: