All patients who went to clinics because of fever in Beijing are required to take nucleic acid tests to see if they are infected with novel coronavirus.

By noon Thursday, the capital had confirmed 150 imported cases of COVID-19 pneumonia, including 12 who have been cured and discharged, according to the Beijing Municipal Health Commission.

Beijing reported a COVID-19 patient on Monday that might have been infected by one of the imported cases in a residential building, according to Pang Xinghuo, deputy director of the Beijing Center for Disease Control and Prevention.

It may be the city's first confirmed case of a local resident being infected by someone arriving in Beijing from overseas, Pang said.

"It's very necessary to have a 14-day concentrated quarantine for inbound passengers because some cases didn't show symptoms of the COVID-19 pneumonia when arriving but had them some time later," Pang said on Wednesday.

The city's anti-COVID-19 group has ordered a thorough investigation on the cause of the infection and is requiring all people now in self-quarantine at home to receive health examinations, according to Beijing's leading group conference on COVID-19 control and prevention held on Wednesday.

Those in self-quarantine should strictly abide by regulations and not leave home before the quarantine ends, it said.

According to Pang, the first such case, confirmed on March 23, might have been infected by a downstairs neighbor who came to Beijing from the United Kingdom on March 5 and was confirmed with COVID-19 on March 12.

The returnee was required to stay at home for self-quarantine but ventured out for activities in the community and to go to a supermarket.

"During that time, they both used stairs in their community building, which might have led to the infection," Pang said.

Since Wednesday, Beijing has required all inbound passengers from other countries and regions, either directly reaching Beijing or transferring from other cities in the country, to undergo concentrated observation and take nucleic acid tests.

Another 713 Beijing citizens or workers who have been held up in Hubei province since the epidemic broke out will return to the capital by two trains on Thursday, Mao Jun, spokesman for the Beijing Major Transport Stations Management Committee, said at a daily news conference on Thursday.

The first batch of such train passengers, a total of 829 people, returned to Beijing on Wednesday, 109 of whom were put under concentrated observation while the rest were sent home for self-quarantine, Mao said.

Expenses incurred for the concentrated observation will be paid by passengers, and fees for transporting them home or to designated facilities will be covered by the government, he added.