TIANJIN -- North China's Tianjin, a municipality that neighbors Beijing, has decided to start a citywide nucleic acid testing after 20 people were tested positive for COVID-19, authorities said Sunday.

The infections were reported from 6 pm Friday to 9 pm Saturday in Jinnan district, and the gene sequencing found the first two locally-confirmed cases were infected with the VOC/Omicron variant, according to the municipal center for disease control and prevention.

It is not confirmed yet whether the infections are related to the imported case of Omicron variant infection in the city.

The citywide nucleic acid testing is expected to complete in 24 hours in four districts from 7 am Sunday and in 12 other districts from 7 am Monday, and residents will not be given a green health code until receiving the negative testing result, the center said.