BEIJING - The Chinese capital on Sunday (June 14) declared an area surrounding a wholesale market "high risk" after dozens of new coronavirus cases emerged, sparking fears of a second wave of infections in the city.

Health authorities reported 44 new coronavirus infections in Beijing, all of whom were linked to the Xinfadi Wholesale Market, which has since been shut down.

All the market's workers and some 46,000 people living in the vicinity will have to undergo testing, authorities said.

Thirty-six of the cases were detected on Saturday during mass testing of market workers while eight new infections were reported early on Sunday.

Many of them were people who had visited the market or were close contacts of those who did, Beijing authorities said, adding that 11 infected people live in the same neighbourhood.

Beijing has entered an "extraordinary period", city spokesman Xu Hejian told reporters during a press conference Sunday (June 14).

All markets, dining outlets and logistics companies countrywide have been ordered to undergo disinfection, said a statement from a coronavirus task force led by Premier Li Keqiang.

With the market very densely populated with a huge movement of people, contact tracing needs to be carried out in the "most stringent" way, noted the task force.

The government has also declared Fengtai, the area where the market is located, to be a high risk area.

Members of the public have been asked to avoid going to the region while those who have visited the market on or before May 30 have been asked to voluntarily take a Covid-19 swab test.

Beijing authorities have put out a list of the areas where the confirmed cases live, as well as a list of their workplaces. They include two restaurants and five markets, as well as a company operating airport buses.

Residents in 11 estates around the market were ordered to stay home beginning last Saturday, with food and groceries being brought to their door by local community workers.

The move harks back to lockdowns enforced in much of China earlier this year when the outbreak was in full swing. Much of the domestic situation has come under control through the strict enforcement of such shut ins, but pockets of cases have continue to surface.

Meanwhile, the National Health Commission said two other local infections reported in China on Sunday were in north-eastern Liaoning province, some 670km away, and were linked to the Xinfadi cluster. A further 19 infections were imported by Chinese returning home from abroad.

Authorities have been quick to reassure Beijingers that their food supply will not be disrupted by the market's closure, saying that there are alternative distribution channels. The city's largest food wholesale market, Xinfadi, is believed to supply nearly 90 per cent of Beijing's fruit and vegetables.

Local media images showed dozens of police and paramilitary officers surrounding the sprawling market on Sunday, which has been barricaded.

That the recent outbreak started in a market has also sparked fresh concerns about hygiene and food safety, especially after traces of the coronavirus were found on a cutting board used for imported salmon at the market.

As a precaution, major supermarkets have pulled the fish off shelves and Beijing has ordered the entire city to undergo a thorough food safety inspection.

It is now imperative to investigate Xinfadi's food supply chain to determine how the virus entered Beijing, said Dr Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention (CDC).

"Beijing has not had any new coronavirus infections for over 50 days... if all the new cases don't have travel history of leaving the city, and have truly been infected here, then it is possible that the imported foods or contaminated foods from outside the city have brought in the virus," he said.

Genetic sequencing of the virus has shown that it came from Europe, according to an expert from the Beijing CDC.

"The preliminary judgement is that the virus was imported," Dr Yang Peng said in an interview with state broadcaster CCTV.

"But it is still unclear exactly how the virus (entered China), it could possibly be from contaminated seafood or meat, or have been carried into the market by people," he said.

How the coronavirus could have spread from a wholesale market

Dozens of coronavirus infections emerging from a Beijing wholesale centre has once again put such markets under the spotlight.

The virus first surfaced late last year at the Huanan Seafood Wholesale Centre, a market in central China's Wuhan, where workers were among the earliest cases.

But unlike the Huanan market, where wild animals were sold for meat, the sprawling Beijing complex sells only agricultural products, supplying up to 90 per cent of the city's vegetables.

Xinfadi, the biggest of such wholesale centres in Beijing, supplies supermarkets, grocery stalls and even small corner stores.

Usually a bustling hive of activity, it is unsurprising the virus resurfaced there because of close interaction and even exposure to imported food items, Dr Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention (CDC), told the official Xinhua news agency.

"With tens of thousands of new cases globally, it could be that an infected person overseas contaminated meat or seafood while handling it," Dr Wu added.

"The virus could have stayed alive longer because of the cool environment, and someone toughing the contaminated produce could have rubbed their noses or eyes after, thus getting infected."

Since the early stages of infection present mild symptoms, it is possible the person continued going to work, thus spreading the virus to others, Dr Wu added.