Beijing reported 42 locally transmitted COVID-19 cases and four asymptomatic cases between 4 pm on Tuesday and 3 pm on Wednesday for a total of 138 infections since Friday involving eight districts, according to senior officials on Wednesday.

"As of 3 pm on Wednesday, the number of cases involving students and children from kindergartens make up 31 percent of the total, across six schools and two kindergartens," said Pang Xinghuo, deputy director of the Beijing Center for Disease Control and Prevention, at a news conference on Wednesday afternoon.

"Among the six schools, a middle school in Chaoyang district registered 36 cases so far," she said. "Schools have a relatively large number of people and some students have been to many places out of school, especially after-school training institutions, which has increased the risk of infection."

On Wednesday, Tongzhou district reported three new cases from three different schools and Fangshan district reported two new cases from a middle school and a childcare institution.

Dong Minghui, deputy head of Tongzhou district, said considering the infection risk, all kindergartens, primary and middle schools, as well as secondary vocational schools in Tongzhou suspended on-campus classes starting Wednesday and began online courses.

All training institutions outside of schools in the district should stop offline courses, she said.

Up to 453 people at risk of infection involved with the cases from schools in Tongzhou would be placed in centralized quarantine. All students and staff from those schools with a total number of more than 6,000 have taken nucleic acid tests on Tuesday. All the results which have come out so far were negative except the cases reported on Wednesday, Dong said.

As the city is taking all measures to control the virus' spread, the city's public security bureau has placed 40 cases on file involving the epidemic since Friday, said Pan Xuhong, deputy head and spokesman of the bureau on Wednesday.

At present, four people were detained for crimes and 48 people are in administrative detention, he said.

A man surnamed Jiang, 26, hid the fact he had deliberately taught at an after-school training institution on Saturday despite being under epidemiological investigation, which caused more than 400 people to be quarantined and around 6,700 residents in eight communities to be put under controlled management. Five people at the training institution, Jiang included, tested positive.