TIANJIN -- North China's Tianjin on Wednesday morning mobilized all residents to undergo the second round of nucleic acid testing, after the first round of citywide screening starting Sunday found 77 positive samples for COVID-19.

The municipality of 13.9 million people that neighbors Beijing launched the first round of citywide mass testing at 7 am Sunday. A total of 11,912,280 people were sampled in the testing drive, and the results of 7,892,591 samples have been released so far.

The infections were first reported on Saturday in Tianjin, and the gene sequencing found the first two locally transmitted confirmed cases were the VOC/Omicron variant, said the municipal headquarters for COVID-19 prevention and control.

The municipal government said in a notice that the second round of mass testing would start Wednesday afternoon, urging all residents to stay put while awaiting the results of their nucleic acid tests.