The coastal city of Huludao in northeastern China's Liaoning Province reported 21 new local COVID-19 cases on Thursday. The provincial governor pledged to step up measures to control the outbreak. The latest resurgence occurred in Huludao's Suizhong county, which has a population of half a million. The county has conducted mass testing on all residents. Schools are shut, public transport is suspended and most businesses are closed. After examining the genetic sequence of the confirmed cases, experts say this outbreak is related to the Delta variant found in cases in the city of Suifenhe, on the border with Russia.