Beijing reported 14 local confirmed cases on Tuesday, all from schools, the Municipal Health Commission said on Wednesday.

One was from the High School Affiliated with Minzu University of China and the rest belong to an infection cluster on the campus of Beijing University of Chemical Technology in the city's Changping district.

The case from the high school was found at the community level, while one infected person in the cluster was found during hospital admission screening. The rest were from quarantine centers.

All have been hospitalized.

The commission added that schools and other crowded places are key areas for epidemic prevention and control, as students return to their campuses from summer vacation.

The city has strengthened multiple measures to avoid infection risks in schools, asking all the schools to tighten the control and prevention measures before the students return and conduct strict health monitoring of the students after their arrival.

"The most prominent feature of colleges is the diversity of students, who are from all over the country and have had complex movements," Hu Yang, associate chief physician of the department of respiratory and critical care medicine at Shanghai Pulmonary Hospital, was quoted as saying by Health Times.

"Students are generally young and have higher immunity to infection. If they were infected, they might not show symptoms and are prone to hidden transmission."

Hu warned that schools should pay close attention to asymptomatic carriers in their efforts to prevent and control COVID-19.