Tianjin, the port city neighboring Beijing, reported 28 cases of COVID-19 infection from Sunday to 6 pm on Monday, officials said on Monday night. Preliminary evidence showed it might be related to imported cold chain food.

The infections were discovered through a citywide nucleic acid testing program conducted on Sunday, with six confirmed COVID-19 cases and 22 asymptomatic carriers registered in the city's Beichen and Dongli districts, Gu Qing, director of the Tianjin Municipal Health Commission, told a news conference.

Gene sequencing indicates they were infected with a version of the Omicron variant different from recent local cases in the city, or from cases from outside.

"Some of the cases have been found to have the experience of working in a cold chain storage in Dongli district," said Gu. "Samples from the outer packaging of food and environment in the storage showed positive."

"We initially judged the latest outbreak were related to imported cold chain food," he added.

The two districts will carry out a new round of nucleic acid testing from Monday to Wednesday.

The city will strengthen the construction of makeshift hospitals and reserve more than 10,000 available beds, said Gu.

Contact the writer at zhouhuiying@chinadaily.com.cn