CHANGCHUN, Jan. 11 (Xinhua) -- Changchun, capital of northeast China's Jilin Province, reported four asymptomatic cases of COVID-19 between midnight Sunday and 8 a.m. Monday, local authorities said.

All the four cases returned from Wangkui County, Suihua City in the neighboring Heilongjiang Province, where new cluster infections were spotted. They were discovered during a voluntary COVID-19 testing and have been rushed to designated hospitals.

All the tracked close contacts and secondary close contacts of the above-mentioned personnel have been put under centralized medical observation, and the places and medical institutions they visited have been disinfected.

The communities they live have tightened management of personnel flow to curb the spread of the virus.