Nearly 10 million people have been tested for coronavirus as part of a three-week blast in Wuhan, where Covid-19 was first discovered last year.
Only 300 positive cases were found with all showing no symptoms, health authorities said.
The city did not find infections among 1,174 close contacts of people who tested positive, suggesting they would not easily spread the virus to others.
This is a potentially stimulating development because of widespread concern that infected people without symptoms could be silent spreaders of the disease.
Feng Zijian, vice director of China & # 39; s Center for Disease Control and Prevention, told state broadcaster CCTV: "It not only eases Wuhan people at their convenience, it also increases people's confidence in China."
There is still no definitive response to the level of risk posed by asymptomatic cases, with hitherto anecdotal evidence and studies that produce conflicting responses.
Wuhan was by far the most hit city in China, accounting for more than 80% of the country's deaths, according to government figures.
A city official announced on Tuesday that the city completed 9.9 million tests from May 14 to June 1.
As the earlier tests are included, virtually anyone over the age of five in 11,000 people in the city has been tested, said Li Lanjuan, a member of an expert team for the National Health Commission.
"The city of Wuhan is safe," she said at a news conference with city officials.
The campaign was launched after a small cluster of cases was found in a residential complex, causing concern about a possible second wave of infections when Wuhan emerged from a 10-week lockdown.
The industrial city on & # 39; the Yangtze River in central China comprises 900 million yuan (about £ 100 million) to & # 39; e tests, said the official Xinhua News Agency.
It quoted executive acting mayor Hu Yabo that the costs were "totally worth" to trust residents, and lift a "psychological lockdown".
Clarence Tam, an assistant professor of public health at the National University of Singapore, said the results are reassuring, but said more information is needed on the value of this type of mass screening when the risk is low.