Medical workers are checking a patient's CT image with a movable CT machine at the "Wuhan Livingroom" makeshift hospital in Wuhan, central China's Hubei Province, Feb. 23, 2020. File photo:Xinhua

Inappropriate disinfection in the CT room at the Qingdao Chest Hospital led to the new cluster of COVID-19 infections in Qingdao, east China's Shandong Province, a local health official said Friday.

Two stevedores who had handled imported frozen seafood at the port of Qingdao were diagnosed as asymptomatic COVID-19 cases on Sept. 24. They were isolated at the Qingdao Chest Hospital and underwent CT scans in the hospital's CT room.

Due to improper disinfection, the CT room was contaminated and the virus further infected other people, Ma Lixin, deputy Party chief of the provincial health commission, told a press conference.

Ma also noted that the new cluster infection was neither caused by nor has caused cross-infection in the community.

A total of 13 new confirmed cases of COVID-19 had been reported in this new wave of infections by Thursday.

Qingdao is conducting a citywide nucleic acid testing campaign covering all of its 11 million residents, with the results expected to be released on Friday evening.