Tianjin finished large-scale nucleic acid testing on all the residents and workers in Hangu Street, Block A and B of the cold-chain logistics area in the central fishing port in Binhai New Area on Wednesday morning.

According to the city's epidemic prevention and control headquarters, samples were taken from more than 65,000 residents and 370 cold-chain workers and all returned negative results for the coronavirus.

The areas were classified as medium-risk for COVID-19 on Tuesday after a 38-year-old man, who works at a loading dock of a cold storage company, tested positive, becoming a confirmed COVID-19 patient on Sunday.

An asymptomatic case of COVID-19 reported on Monday was diagnosed with the confirmed case on Wednesday, the city's epidemic prevention and control headquarters said.

The patient is a 47-year-old man who drove to the company and loaded frozen food on Nov 5.

During the quarantine period at Haihe Hospital, he appeared to have symptoms of fever, dry throat and heavy sweating.

Then he was diagnosed as a confirmed case in mild condition after expert consultation.

The city's disease control and prevention center immediately started epidemiological investigations after a 38-year-old patient was confirmed on Sunday.

Results showed that the confirmed case might have become infected due to contact with goods contaminated by novel coronavirus, a local official told CCTV News.

"The confirmed case hadn't been to the areas of the COVID-19 epidemic outbreak or had contact with other COVID-19 patients," said Liang Chunzao, deputy director of Binhai New Area. "And the asymptomatic case reported on Monday had no direct contact with the confirmed case. The only correlation between them is the cold storage."

The results also showed that the type of the novel coronavirus of the local case was highly similar to the strain that spread in North America from March to June. It is Branch II (North American branch) of the European L genotype.

"He hadn't been overseas or had contact with people from overseas," he said. "Therefore, all the evidence demonstrated he was infected by the goods."

"However, it still needs further investigation to judge whether the confirmed case and the relevant asymptomatic case were infected by the same goods."