BEIJING - A wholesale food market in south-west Beijing is in the spotlight after being linked to a spate of new Covid-19 cases, sparking fears of a second wave of infections.

City authorities swiftly shut the Xinfadi market, which is the largest in the capital city, in the early hours of Saturday morning.

Mass testing was ordered after an outbreak was detected among shoppers and workers there.

Officials said at a news briefing on Saturday (June 13) that there have been six cases reported on Friday, all related to the market which sells meat, seafood, fruit and vegetables.

Another man who had shopped there was also reported as a confirmed case on Thursday.

In addition, 45 people also tested positive from among 517 samples collected at the market, although none have shown symptoms of the coronavirus infection. China does not include asymptomatic cases in its official tally.

"These cases may have contacted the contaminated environment in the market or been in contact with infected people. More cases cannot be ruled out in the future," said Beijing Centre for Disease Control and Prevention deputy director Pang Xinghuo.

“For this reason, it is absolutely necessary to close the Xinfadi market. Contact tracing is still going on.”

Another case, although asymptomatic, was found in a farmers’ market in the northwest district of Haidian, prompting authorities there to order restaurants to re-introduce social distancing measures and cancel bookings involving large groups.

The first outbreak of Covid-19 is believed to have originated from the Huanan seafood market in Wuhan, in Hubei province.

Fengtai district, where the Xinfadi market is located, has gone into “wartime mode”, said its acting mayor Chu Junwei on Saturday.

He has ordered 11 residential compounds around the market to be put under quarantine. Three schools and six kindergartens nearby were also closed.

Health authorities are now testing 10,000 workers in Xinfadi market, while disinfecting the place, which spans 112 hectares and supplies as much as 90 per cent of the city’s fruits and vegetables.

Nucleic acid testing extends to close contacts of the workers or visitors of the market going back to May 30.

Beijing had managed to keep a clean record for nearly two months. City authorities had lowered the four-tier emergency response to Level 3 just last week.

But last Thursday, a 52-year-old man became the city’s first confirmed Covid-19 case in 56 days. He had shopped at Xinfadi market on June 3 and later developed a fever.

On Friday, the city identified another two locally transmitted cases, both of whom work at a meat products research institute. One of them visited Xinfadi market on June 5.

All their close contacts have been tested and put under quarantine.

Workers will disinfect the market while at least three other temporary markets have been set up to ensure supply is not disrupted.

Fearing a second wave of infection, city authorities have quickly restored stricter measures. Lower primary students, who were supposed to return to school next Monday (June 15), have been told classes are cancelled until further notice.

All sporting events have also been halted.

Meanwhile, health officials are conducting sweeping checks of food markets, warehouses, catering services and restaurants, as well as inbound cargo flights. Since Saturday morning, operations at six major wholesale markets in Beijing have been fully or partially suspended.

Chinese news outlet Beijing News reported that the virus was detected on a chopping board for imported salmon at Xinfadi market, and had come from Jingshen seafood market,one of the markets ordered shut on Friday.

Large supermarket chains such as Carrefour and Japanese restaurants have pulled salmon off the shelves and menus after news that salmon supplies could be contaminated sparked worries across the city.