Beijing and Dalian, Liaoning province, have tightened the supervision of imported frozen food amid the recent outbreak of COVID-19 infections, especially after an epidemiologist spotted the similarity of the two cities in seafood markets or processing.

Dalian has increased its screening of imported aquatic products, frozen and refrigerated meat and other key products, and has also strengthened the daily supervision of storage facilities and markets, said Zhao Lian, deputy director of the city's health commission, on Thursday.

Beijing will also strengthen oversight of imported cold-chain food by accelerating the formulation of standards in the sector, along with a tracing system, according to a statement from the capital's anti-virus leading group on Wednesday.

The two cities have experienced recent outbreaks of COVID-19, with similar origins.

In Beijing, the infections were related to the Xinfadi wholesale food market; in Dalian, many confirmed cases have been connected to people working at Kaiyang World Seafood Co.

Further, the outbreak in Wuhan, capital of Hubei province, in January was tied to the Huanan seafood market.

"The three places all have moist, low-temperature environments," Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, told CGTN in a TV program in Chinese on Wednesday night.

That type of environment is suitable for the survival of the virus, he said. When there is contamination, the virus can accumulate in certain areas and is not easily killed, so there's a risk of transmission, he said.

According to Wu, Dalian has identified no new local COVID-19 cases for more than 100 days. The virus must have come from outside.

Big data analysis has not established a definite relationship between the epidemic in Dalian and the outbreak in Beijing, he said, nor is there any definite indication of a connection with imported cases from abroad.

"It is more likely to have been imported via contaminated seafood from abroad," Wu said.

China reported 102 new locally transmitted cases of COVID-19 infections on Wednesday. Ninety-six were reported in the Xinjiang Uygur autonomous region, five in Dalian, and one in Beijing, according to National Health Commission.

Based on recent data, China had 400 locally transmitted cases from July 23 to 29.

But the latest outbreak in Dalian has been basically contained, and no further large-scale spread is expected, Wu said.

"Because of the timely quarantine, there is no great risk of transmission," he said.

Since Sunday, Dalian has been arranging free coronavirus tests for all of its residents. As of Wednesday, about 4.1 million samples had been collected, said Zhao Lian from the city's health commission.

In Urumqi, capital of Xinjiang, the city government highlighted the strengthened management on people leaving the city to contain the spread of infections, like the need for 14-day quarantines in the city and negative nucleic acid test results, said the city's Deputy Mayor Song Yajun on Thursday.

In addition, the city government decided to increase the supply of meat and vegetables for the city's Muslims, who are preparing to celebrate the Eid-al-Adha holiday on Friday, Song said.

"The butchering in Urumqi will be accelerated during the holiday, and the city will provide abundant foods, including more fresh meat and vegetables on the market with fair prices," he said.

According to Song, the city's government has been guiding to stabilize the market prices of daily needs since July 24, and nearly 20 million yuan ($2.8 million) of financial subsidies have been put in place.