BEIJING — State media say one of China’s most serious recent outbreaks of COVID-19 partly stemmed from people gathered at mahjong parlors and at a virus testing site.

The city of Yangzhou in the eastern province of Jiangsu added another 54 confirmed cases on Wednesday, bringing its total to 448 since the outbreak spread from the international airport in the provincial capital of Nanjing on July 20.

Reports said the cluster has been traced partly to a 64-year-old woman who visited several mahjong parlors after returning from Nanjing and was positive for the virus during mass testing following the outbreak.

Dozens of others were infected at a testing site in the village of Lianhe on the outskirts of Yangzhou, the ruling Communist Party newspaper People’s Daily said. While China has imposed stiff rules on testing, lockdowns and mask wearing, test sites in Beijing and elsewhere have experienced crowding and relatively little social distancing.

China currently has 1,789 COVID-19 patients in treatment, 666 of them in Jiangsu. The country has reported a total of 94,080 cases and 4,636 deaths from the illness since the first cases in the pandemic were discovered in the central Chinese city of Wuhan in late 2019.