The city has recorded new 158 infections since confirming the first on June 11 in its worst outbreak since early February. It is thought the outbreak originated from the wholesale food centre of Xinfadi in the South West of the city.
One journalist said he received a phone call ordering him to get tested after he attended the “sprawling” market.
Photographer Mark Schiefelbein told how he was tracked via his phone.
He added: “After word first emerged of a cluster of cases at a sprawling wholesale market in the Chinese capital, I had gone to the area to take photographs.
“Although I never entered the Xinfadi market and only took photos from nearby streets, unknown to me, I had been flagged as a potential vector for the virus.
“My phone rang on Wednesday afternoon. An official from my neighbourhood’s community association informed me that I should shortly report to the gates of a nearby sports stadium to be bused to a coronavirus testing site.”
All of Beijing’s 21 million residents have been placed under a strict lockdown as imposed in the central city of Wuhan where the virus first emerged late last year.
Under the policy, residents of 32 neighbourhoods designated medium-risk and one area deemed high-risk have been barred from leaving the city.
Meanwhile, residents of low-risk areas must show proof of negative disease tests in order to leave the city.
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Wu Zunyou, the chief epidemiologist of China’s Center for Diseases Prevention and Control, added: “The epidemic in Beijing has been brought under control.
“When I say that it’s under control, that doesn’t mean the number of cases will turn zero tomorrow or the day after.
“The trend will persist for a period of time, but the number of cases will decrease, just like the trend that we saw (in Beijing) in January and February.”
Mr Schiefelbein, added: “The caller did not know my name, but they knew that someone associated with my cellphone number had been in the vicinity of the market. I may have been tracked through my cellphone.
“A Beijing city official said Wednesday that 355,000 people have been identified for testing via big data, but he did not specify how.”