BEIJING — The central Chinese city of Wuhan has tested nearly every one of its 11 million people for the coronavirus in a mass effort that resulted in the isolation of 300 people, authorities said Wednesday.

The pandemic is believed to have originated last year in the industrial city that went under lockdown for 76 days to try to stop the outbreak. Wuhan still accounts for the bulk of China’s 83,021 cases and 4,634 deaths from the disease.

The testing effort carried out in the second half of May targeted every resident not already tested and excluded only children under age 6.

“This is extraordinarily rare anywhere in the world,“ National Health Commission expert Li Lanjuan told reporters. “It not only shows confidence and determination in the fight against the epidemic in Wuhan, but has also provided reference to other cities for their prevention.”

No new cases of COVID-19 were found, although 300 people who tested positive for the virus without showing symptoms were placed in isolation.

The executive deputy mayor, Hu Yabo, said the city spent 900 million yuan ($126 million) on the tests, a “totally worthwhile” expenditure as Wuhan looks to reassure residents and people elsewhere in China and get the city’s local economy humming again, the official Xinhua News Agency quoted him as saying.