Authorities in Wuhan, China said they would test its entire population for Covid-19 after the city reported its first local infections in more than a year.
Authorities announced on Monday that seven locally transmitted infections had been found among migrant workers in the city, breaking a year-long streak without domestic cases after it squashed an initial outbreak with an unprecedented lockdown in early 2020.
China has confined the residents of entire cities to their homes, cut domestic transport links and rolled out mass testing in recent days as it battles its largest coronavirus outbreak in months.
China reported 61 domestic cases on Tuesday as an outbreak of the fast-spreading Delta variant reached dozens of cities after infections among airport cleaners in Nanjing sparked a chain of cases that have been reported across the country.
Major cities including Beijing have now tested millions of residents while cordoning off residential compounds and placing close contacts under quarantine.
China had previously boasted of its success in bringing domestic cases down to virtually zero after the coronavirus first emerged in Wuhan, allowing the economy to rebound.
But the latest outbreak is threatening that success with more than 400 domestic cases reported since mid-July.
Wuhan, the city of 11 million people had been in the news since late 2019 when it was the epicenter of the COVID-19 outbreak that later spread around the world.
Though it is widely accepted that the pandemic spread from the illegal wet markets of Wuhan, China has so far stopped short of accepting this and has done everything it can to suggest that the virus was circulating around the world before it was 'first discovered' in the city.
China had and still to a large extent has blocked any detailed investigation into the origins of the virus, including the possibility of it leaking out of the Wuhan Institute of Virology, where Chinese scientists were studying Coronaviruses.
On Monday, a report released by US Republicans claimed that there was ¡°ample evidence¡± that WIV scientists ¨C aided by US experts and Chinese and US government funds ¨C were working to modify coronaviruses to infect humans and such manipulation could be hidden.