China is starting mass testing on three million people in a section in the northern city of Tianjin and has tested 4015 people in a hospital in Shanghai after the discovery of a few cases on Friday.
The National Health Commission recorded seven new domestically transmitted cases of COVID-19 on Saturday, with five in Tianjin and two cases in the city of Shanghai.
Tianjin on Friday reported a case of community transmission involving four individuals.
In response, authorities sealed off the residential community where the individuals lived as well as a hospital and a kindergarten.
Authorities started testing all residents in Binhai district in Tianjin city on Saturday, local authorities said.
In Shanghai, authorities sealed off a hospital after a husband and wife in Shanghai's Pudong New Area tested positive for COVID-19 Friday night after visiting the hospital for a diagnosis.
The last local coronavirus infection in Shanghai was reported on November 9. Before that, the last confirmed local case was on June 29 as measures aimed at stopping an alarming spread of the virus in the city proved successful.
China's number of confirmed COVID-19 cases is now 86,414, while the death toll remains at 4634.