Beijing confirmed two new cases of the novel coronavirus on Friday. Two employees working at China Meat Research Center in the Fengtai District have contracted the virus.

This comes a day after one case was detected on Thursday in Beijing's Xicheng District after 56 days of zero local transmission.

Read more: Beijing registers one new confirmed COVID-19 case: Official

One of the new patients, a 25-year-old man surnamed Liu, has a travel history in the past two weeks. He spent five days in Qingdao, east China's Shandong Province.

He said he has had no contact with people coming from abroad or from Wuhan City in Hubei Province, according to the municipal authority.

Liu first developed a cough, a fever, sneezing and a sore throat on June 9. His nucleic test result came back positive on Friday.

His colleague, a 37-year-old man surnamed Yin, also had a cough on June 9 but no fever. Yin had no record of recent outbound travel, nor contact with people from abroad and Wuhan.

Sources of new infections unknown

It was not immediately clear how the three men were infected. Two of the three new cases had no recent travel history outside of Beijing.

Later on Friday, the Qingdao Health Commission ruled out the possibility of Liu's infection in Qingdao. He is the only man with a travel history outside Beijing in the past 14 days.

"Liu came to Qingdao on May 29 and returned to Beijing on June 2. As of today, he has been away from Qingdao for 10 days. Experts from the Department of Disease Control and Prevention in our city have ruled out the possibility of his infection in Qingdao," the statement said.

Liu, who works in product sampling, was in Qingdao for business. He had been to four local markets.

Major markets closed and school returns delayed

Authorities Friday also revealed details of Thursday's new case and disclosed his travel history since May 31.

The Xicheng District resident visited several public venues in Fengtai, including a grocery store, a shopping mall and a supermarket.

Xinfadi Wholesale Market, one of the places he went to, has been partially closed and another seafood market in Fengtai that Friday's new patients have reportedly visited was also closed on Friday, according to local media Beijing News.

Except for the two, four other major wholesale food markets across Beijing were either wholly or partially shut in light of the new cases, Beijing Youth Daily reported.

The municipal government later said restaurants would be inspected and checks made on seafood products and fresh and frozen meats.

On the same day, education officials in Beijing also announced classes of grades one-three in all primary schools would not reopen next week on June 15 as planned.

Around 520,000 students will be affected.

Read more: Beijing suspends class resumption after new COVID-19 cases

Testing and quarantine underway

Following the detection of new cases on Friday, the Fengtai District authority said closed-off management would be activated in the communities in which the two patients live, and 43 close contacts have been quarantined as of Friday afternoon.

Throat swabs have been collected from them for nucleic acid tests.

The authority also revealed that among all 38 close contacts of Thursday's patient, 23 have been put into group quarantine, a one-year-old infant is now being isolated at home and the other 14 people are being moved to centralized quarantine.

Nucleic tests for 21 out of the 38 people have come out negative so far.

33 classmates and 15 school staff linked to the patient's child have all been tested, none of whom have contracted the coronavirus.

Xicheng District said on Friday night that it has conducted environmental tests to the places the patient had been to, results from five locations came back negative so far.