The mine is in Mojiang in southwest China, about 1,500 kilometres from Wuhan, where COVID-19 was first identified.
According to the Wuhan Institute of Virology's Shi Zhengli, China's top bat coronavirus researcher, the workers' pneumonia-like symptoms were caused by a fungal infection.
First identified in 2016, RaTG13 shares 96.2% of its genome with SARS-CoV-2, according to a paper released by Shi and other researchers early in February 2020, just weeks after the first COVID-19 cases had been identified in Wuhan.
The institute in November 2020 disclosed the existence of eight other "SARS-type" coronavirus samples taken from the site.
The paper concluded that "the experimental evidence cannot support" claims that SARS-CoV-2 was leaked from the lab, and called for "more systematic and longitudinal sampling of bats, pangolins or other possible intermediate animals" to better understand where the pandemic originated.
A report on the origins of Covid-19 by a US government national laboratory concluded that the hypothesis claiming the virus leaked from a Chinese lab in Wuhan is plausible and deserves further investigation, according to a report.