Nanjing, Jiangsu province, had upgraded 10 of its communities from low- to medium-risk for COVID-19 as of Thursday morning.

The city reported nine confirmed cases and eight asymptomatic carriers on Wednesday after workers at Nanjing Lukou International Airport tested positive for the coronavirus.

Citywide testing of 9.3 million residents has been underway since Wednesday. People lined up and waited all night across the city for samples to be taken.

Jiangning district, the downtown district where the airport is located, set up 551 testing centers and finished testing its 1.9 million residents in one day, according to the local information office.

Anyone wanting to leave the city, either by train, plane or bus, must present a negative result for a test taken within 48 hours.