Nanjing, Jiangsu province, reported two locally transmitted COVID-19 cases and two asymptomatic carriers on Saturday.

As of early Sunday morning, a total of 37 locally transmitted cases were undergoing treatment at the city's designated hospital for COVID-19, while 21 asymptomatic carriers were under medical observation, according to provincial health commission.

Presently, Jiangsu has 1,318 contacts of the infected patients and asymptomatic carriers under medical observation.

On Tuesday, some samples collected from employees of Nanjing's Lukou International Airport tested positive for COVID-19. Many workers, mostly in the cleaning and ground services departments, have tested positive for the virus since then.

The city has launched a second-round of citywide nucleic acid testing of its 9.3 million residents and travelers starting Sunday morning.

It has also set up 68 checkpoints on roads around the city to guarantee that all travelers leaving Nanjing can present a negative nucleic acid testing report taken within 48 hours.