Full virus gene sequencing results showed the virus from the asymptomatic COVID-19 cases and food packaging in Dalian, Liaoning province belongs to a subtype of the L genotype of the European family branch, an official with the city's health commission said at a news conference on Friday.

"The homology of the whole genome sequence of asymptomatic cases was 100 percent, indicating the source of the outbreak came from overseas," said Zhao Lian, deputy director of Dalian's health commission.

Since the port city reported its first four asymptomatic cases on Tuesday, it reported two new asymptomatic cases on Thursday. All are workers at a labor dispatching company named Haohan. They were engaged in unloading imported cold food for Dalian Port Yidu Cold Chain.

All six infected persons are in stable condition, Zhao said.

The factory of Yidu Cold Chain and a nearby residential community where they lived are divided into two controlled areas and strict closed management is being implemented, she added.