Continuing efforts are being made in Qingdao, Shandong province, to curb the latest outbreak of COVID-19, as more confirmed and asymptomatic cases from a cluster centered at a middle school have been reported.

In the 12 hours ending at noon on Tuesday, Laixi, a county-level city under Qingdao's jurisdiction, reported 12 more confirmed cases and 63 asymptomatic carriers.

By noon, 175 locally transmitted COVID-19 cases had been confirmed, along with 305 asymptomatic cases, due to an outbreak at Laixi's No 7 Middle School since Friday. Most of those infected are students and teachers.

The city, about 100 kilometers from downtown Qingdao, started its second round of mass testing on Monday. A total of 584,109 swab samples have been collected from residents, Sui Ruwen, vice-mayor of Qingdao, said at a news conference on Tuesday morning.

Of those, 62 had come back positive so far, Sui said, adding that the people's contacts and secondary contacts would be observed.

He said that all-out efforts are being made to help coronavirus patients recover, as epidemiological investigations and source tracing continue.

The outbreak in Laixi came to light on Friday night, when the local health authority confirmed that three students were infected. The round of testing that followed in Laixi, as well as other tracing actions, found a number of infections.