A district of Beijing is on a "wartime emergency" footing and tourism has been banned in the Chinese capital after a spike in coronavirus cases centred around a food market has sparked fears of a fresh outbreak. The move comes amid mounting concern over a second wave of the COVID-19 pandemic. Eleven neighbourhoods around the wholesale market in the city's southwestern Fengtai district have gone into lockdown, where an official said it was in "wartime emergency mode". An official has said the area is in 'wartime emergency mode' The cluster was detected after throat swabs from 45 people, out of 517 tested at the district's Xinfadi market, proved positive for coronavirus, although none of them showed symptoms of COVID-19, according to the authorities. Officials have said more than 10,000 people at the market will be tested, and the premises disinfected. A city spokesman said all six COVID-19 patients confirmed in Beijing on Friday had visited the market. They are the first locally transmitted cases in the city in more than 50 days. More from Covid-19 Coronavirus: Aquariums under threat after being excluded from reopening plans Portugal: 'Europe's dumping ground' suspends waste imports over landfill concerns Coronavirus: Brazil overtakes UK with world's second-highest number of COVID-19 deaths Coronavirus: New documents reveal what the next step for social bubbles could be Coronavirus: Racism has contributed to COVID-19's disproportionate impact on BAME community, leaked report shows Coronavirus: All Saints fashions CVA plan amid high street crisis Health officials in surrounding districts have also been asking residents whether they have visited the Xinfadi market. The Xinfadi wholesale market has been closed following the spike in infections Image: The Xinfadi wholesale market has been closed by the authorities The market was closed after someone, who had recently visited it, was reported to have been infected on Thursday. As well as halting domestic tourism, sporting events have also been suspended in the city, while plans to reopen schools for some students have been dropped. Pang Xinghuo, an official at the Beijing Centre for Disease Control, said: "Preliminary judgement suggests these cases may have come into contact with a contaminated environment in the market, or were infected after being in contact with infected people. "We cannot rule out subsequent cases in the future." Coronavirus: Infection numbers in real time Coronavirus: Infection numbers in real time Sky's Asia correspondent Siobhan Robbins said: "People in the area have been told not to leave their houses. "It is a worrying time for Beijing because it hadn't had a locally transmitted case for almost two months, so it just shows you how tricky COVID-19 is to keep under control, and Beijing isn't taking any chances. "Not only are these areas in lockdown, some schools and nurseries in the area were closed on Friday, several other markets have been shut as well. "There is mass testing taking place, officials saying that more than 2,000 wholesale market workers were tested on Friday alone. "State media are reporting that the chairman of the market said traces of COVID-19 were found on a salmon chopping board - that has led to people getting concerned about food safety standards and an investigation launched across the city," she added. The virus was first reported at a seafood market in Wuhan, the capital of central China's Hubei province, in December. There have now been around 7.6 million people infected worldwide and more than 420,000 have died, according to Johns Hopkins University which has been tracking the outbreak.