Tianjin finished nucleic acid testing of all residents and workers in the city's medium-risk areas on Wednesday morning, with the results all negative for novel coronavirus infection.

The city's epidemic prevention and control headquarters said samples from more than 65,000 Hangu subdistrict residents and 370 cold-chain workers in blocks A and B of a cold-chain logistics area in the central fishing port in Binhai New Area had been tested since Monday night.

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

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

The second patient is a 47-year-old male driver who picked up a load of frozen food from the cold storage company on Nov 5.

The city's disease control and prevention center immediately started epidemiological investigations after the first case was confirmed on Sunday. The results showed that the type of novel coronavirus in the two cases was very similar to the strain that spread in North America from March to June, the center said.

Results also showed that the first confirmed case might have been infected through contact with goods contaminated by the novel coronavirus, a local official told China Central Television on Tuesday.

"The (first) confirmed case hadn't been to areas with a COVID-19 out-break, nor had he been in contact with other COVID-19 patients," Liang Chunzao, deputy director of Binhai New Area, told CCTV. "And the asymptomatic case reported on Monday had no direct contact with the confirmed case. The only correlation between them is the cold storage."

Meanwhile, the Zhangyang residential community in Yingshang county, Fuyang, Anhui province, was classified as a medium-risk region for COVID-19 epidemic control on Wednesday afternoon, the local epidemic prevention and control headquarters said.

On Tuesday, the city reported a confirmed COVID-19 case, a 50-year-old cargo handler at Shanghai Pudong International Airport who is a close contact of a confirmed case reported in Shanghai on Monday.

The cargo handler took a coach to Yingshang county and then a minibus home on Nov 5. He was confirmed as a positive case on Tuesday after he was transported to a hospital in Fuyang for isolation.