Dalian, Liaoning province, will carry out nucleic acid testing for 190,000 people in areas related to confirmed cases and will expand to cover more where mobile transmission is possible, a senior government official said on Thursday.

Luo Weixing, deputy secretary-general of the Dalian municipal government, said at a news conference on Thursday that the city will conduct thorough testing of all people living in places at risk of exposure to new confirmed cases.

Dalian reported two more local COVID-19 cases and 12 asymptomatic infections on Thursday after one local case was reported on Wednesday, local health authorities said.

"About 111 days have passed since the city's latest new locally transmitted COVID-19 case was reported," said Zhao Lian, deputy director of the Dalian Health Commission.

The 12 asymptomatic infections were discovered when the subjects were being checked as close contacts of the first case. They are coworkers at the same workshop of a seafood processing factory.

Zhao said the factory's seafood processing plant, cold storage and 18 directly operated stores had been closed. Local authorities collected food and environmental samples in the factory's workshops, office buildings, dormitories, catering rooms, toilets and other places.

Some of the samples tested positive for the novel coronavirus.

Three confirmed patients said they had not left Dalian within 14 days of the onset of the disease, had no contact with any confirmed COVID-19 patient or people at risk in key areas.

Dalian is making rapid, efficient, scientific and orderly progress in epidemic prevention and control, the authorities said.