The border city of Manzhouli, north China's Inner Mongolia Autonomous Region, reported 12 locally transmitted confirmed COVID-19 cases from 12 a.m. to 2 p.m. on Wednesday, local authorities said.

Five areas in the county-level Zhalainuo'er District, where 19 new local infections were logged on Tuesday, have been classified as medium-risk areas for COVID-19 infections starting 8 p.m. Tuesday, local authorities said Wednesday.

The city has three high-risk areas and six medium-risk areas.

The city's latest outbreak was preliminarily believed to be caused by coronavirus on imported goods, said Wang Tao, vice mayor and head of the Public Security Department of Manzhouli, during a press briefing on Tuesday.

A total of 57 positive cases were detected in the third round of mass testing in Manzhouli, which concluded on Wednesday.