Eleven more districts began testing on Tuesday.
The testing order for Chaoyang sparked panic buying from Sunday night, with residents lining up at supermarkets with full carts and bulging shopping bags as state media tried to reassure the public that there were plentiful supplies.
Beijing residents told AFP they feared a repeat of the sudden lockdown in Shanghai, where people have struggled to obtain food and medical care for non-Covid conditions.
City health official Xu Hejian said Monday that the spread of the virus in Beijing was still "within the scope of control".
The capital reported 33 new cases on Tuesday, a fraction of Shanghai's daily tally of 16,000.
But Beijing officials are anxious to avoid a spiralling outbreak.
They have urged companies to allow employees to work from home, sealed off multiple residential areas and suspended local group tourism ahead of the long 1 May national holiday.
Authorities on Monday urged Beijing residents not to leave the city for these holidays unless necessary.
Beijing's measures are mild, however, compared with actions taken elsewhere, Pinpoint Asset Management chief economist Zhiwei Zhang said in a note.
"I am surprised that the government did not impose restrictive policies in Beijing as harshly and quickly as in other cities that experienced similar outbreaks in recent weeks," he wrote.
Under its zero-Covid policy, China has used strict lockdowns, mass testing and severe travel restrictions to stamp out infections.
But authorities are increasingly struggling with the impact of these protocols on the economy and business morale, especially when outbreaks appear in the country's most important cities.
Concerns have grown around the world about how the outbreaks in China and its government's anti-Covid policies could impact the global economy, especially supply chains.
The city of Baotou in the country's Inner Mongolia region -- a major supplier of rare earths -- said Monday that after the detection of two virus cases, all residents must stay home, with each household only sending one member out to buy necessities once a day.
That order came as Shanghai's lockdown dragged on, with social media users and local news outlets sharing images of green metal fences put up across the city to keep residents confined to their buildings.
One viral image appeared to show fences along the deserted pavements of a once-bustling street where restaurant patrons used to dine al fresco.