Tianjin, a major Chinese port city near the capital Beijing, has begun mass-testing its 14 million residents after a cluster of 20 children and adults tested positive for COVID-19, including at least two with the Omicron variant, writes The Guardian.

Those infected include 15 students aged between eight and 13, a staff member at an after-school centre and four parents. The citywide testing, begun on Sunday, is to be completed over two days.

The first two cases confirmed in Tianjin were a 10-year-old girl and a 29-year-old woman working at the after-school centre. Both were infected by the Omicron variant. In subsequent testing of close contacts, 18 others tested positive and 767 tested negative as of Saturday night.