Six locally transmitted COVID-19 cases were reported in Shanghai on Thursday, the city government announced on Friday morning.

The first case is a 56-year-old man who is a logistics worker at the Shanghai Cancer Center Affiliated with Fudan University in Xuhui district.

Contact tracing for this individual led to the discovery of another two cases –a 48-year-old female friend and a 53-year-old neighbor who is a worker at the west branch of Renji Hospital Affiliated with Shanghai Jiao Tong University Medical School in Huangpu district.

The Zhaotonglu residential neighborhood in Huangpu district where the three confirmed patients live has been categorized as a medium-risk area.

Contact tracing led to the discovery of the next three cases.

A total of 74 Shanghai-based close contacts of the confirmed cases have already been identified and placed under hotel quarantine as of 10 pm on Thursday. The 86 close contacts of those who were in close contact with the confirmed cases have also been identified.

More than 15,000 individuals have been screened. All have tested negative for their first nucleic acid test.

All public venues visited by the confirmed cases over the past 14 days, including a hotel, eateries, a grocery store, a convenient store, and a drug store - all of which are located in downtown Huangpu district - have been disinfected.

"The first three cases were found during regular nucleic acid tests that medical institutions administered to their staff. Two of them worked in hospitals and the other was a friend of one of them," said Wu Jinglei, director of the Shanghai Municipal Health Commission.

The fourth case is a relative of the second case. The fifth case lived in the hotel that the third case works at. The sixth case is a colleague of the third case.