Beijing will strengthen COVID-19 epidemic control and measures to prevent the rising risk of infection caused by students returning to their campuses from summer vacation, a senior official said at a news conference on Tuesday.

The Beijing University of Chemical Technology reported one locally transmitted COVID-19 case and five positive cases between midnight and 10 am on Tuesday, said Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control.

The confirmed case is that of a college student who returned to the city from another province for the new semester. The student, whose nucleic acid tests on Aug 29, 30, 31 and Sept 2 showed negative results, tested positive on Monday and has been sent to the designated hospital for medical treatment after developing a fever.

The other five cases are students who were close contacts of the confirmed case. They also tested positive on Tuesday, but have no symptoms and are under observation, Liu said.

The student whose case was confirmed took the G572 train on Aug 28 and arrived in Beijing at noon. After arriving at the school that afternoon, the student had not left the campus until being transferred to a hospital after developing the fever on Monday.

"This latest infection cluster located in the college is a warning that the infection risk is increasing as many students are returning from summer vacation," Liu said. "Beijing's epidemic control and prevention condition is severe at present."

Wang Feng, vice-principal of the Beijing University of Chemical Technology, said at the same news conference that all staff members and students who are considered at risk have been sent to centralized quarantine.

The college has three campuses in Beijing. In addition to the one in Changping district where the cases were reported, the college authority has also tightened epidemic control and prevention measures at the other two campuses, in Chaoyang and Haidian districts, he said.

"The college has started online teaching and suspended all group activities," he added.

The No 4 building of the campus in Changping district, where the students live, has been designated as a high-risk area.

Li Yi, spokesman of the Beijing Commission of Education, said the city has strengthened multiple measures to avoid infection risks in colleges, asking all the colleges to tighten the control and prevention measures before the students return and conduct strict health monitoring of the students after their arrival.

"At present, around 230,000 college teachers and students are gradually returning to Beijing for the new semester. During this period when many places in China have epidemic outbreaks, the control and prevention condition is complicated, so the measures should be strengthened," Li said.

Beijing also reported one locally transmitted COVID-19 case on Monday. The person, who lives in Fengtai district, was in quarantine for observation when their case was confirmed.

Xu Hejian, spokesman for Beijing municipal government, said people from cities or counties where there are one or more confirmed cases reported in the previous seven days should not come to Beijing. "People who have entered Beijing should not go to crowded places or gatherings for seven days," he added.