Tianjin reported a new asymptomatic case of COVID-19 on Tuesday afternoon, according to the city's disease control and prevention center.

The patient is a 48-year-old male stevedore in the Tianjin Dongjiang Free Trade Port Zone in Binhai New Area.

He was found to have tested positive for coronavirus during nucleic acid testing for workers of all cold storage and cold-chain companies across the city on Tuesday morning.

The center got the same result from the re-examination.

Then he was diagnosed as an asymptomatic case.

All 14 of the patient's close contacts have been transported to a designated site for isolation.

A massive nucleic acid test is underway for 77,000 residents in Hangu Street, Block A and B of the cold-chain logistics area in the central fishing port in Binhai New Area. It began Monday evening.

The three regions were classified as medium-risk regions of COVID-19 epidemic control beginning Tuesday.

As of Tuesday morning, 51,000 samples had been collected to test for the novel coronavirus, covering 11 communities in Hangu Street.

"The overnight tests went smoothly and we have teamed up with staff members in epidemic prevention to help conduct the tests for some elderly in our community," said Li Haiyan, Party secretary of Dongbinli community, which is home to a population of 3,000.

"We received notice that we can rest at home until we get negative results," said resident Wang Gang. "I think it can soothe our stress, as well as colleagues in our companies."

Officials also urged residents in the medium-risk regions not to leave those regions.

Those who have to leave for special reasons must provide negative nucleic acid test results within seven days before leaving and will be asked to avoid public transportation.

The type of the novel coronavirus of the latest local COVID-19 case in Tianjin was highly similar to the strain that spread in North America from March to June, local government said on Tuesday morning.

It is Branch II (North American branch) of the European L genotype.

A 38-year-old man, who works on a loading dock at the cold storage company, was confirmed as the 138th local COVID-19 case on Sunday.

On Sunday, the city's disease control and prevention center started analysis based on the respiratory specimens of the case in Tianjin and the relevant cold storage environment. Experts got the results on Monday.

He tested positive on Sunday after he was found to have handled a shipment of frozen pork on Wednesday.

Samples of the outer packing of the pork, which arrived in Tianjin on Oct 19 from Germany, tested positive for coronavirus on Saturday after being sent to Dezhou, East China's Shandong province, testing of all places where it had contact.

On Monday afternoon, the city reported a new asymptomatic case of COVID-19, a 47-year-old male driver who drove to the company and loaded frozen food on Nov 5.

During the nucleic acid testing for workers of all cold storage and cold-chain companies across the city on Monday morning, a mixed sample, including one human specimen and two food surfaces, tested weakly positive, the city's disease control and prevention center said on Tuesday.

Several relevant markets in Nankai district have been temporarily closed and relevant people were sent to designated hospitals for isolation.

Then the district's disease control and prevention center re-examined the results, all of which were negative.

Further tests and reviews are ongoing.

On Monday evening, Gengma Dai and Va autonomous county reported two new asymptomatic cases of COVID-19.

During the nucleic acid testing in some areas of Mengding Town, two Burmese people were found to have tested positive for coronavirus.

They were diagnosed as asymptomatic cases after expert consultation.

The province also reported a new imported asymptomatic case that came to Ruili from Myanmar on Tuesday.

Gengma launched emergency prevention action on Monday evening.

Residents in three communities of Mengding town, including Baqu, Qingshuihe and Banxing, were required to complete a 14-day quarantine at home.

All students and teachers in 66 schools of Mengding town and Mengding farm were also asked to stay at home and suspend their return school.