This would not be unprecedented. In 2004 two researchers in Beijing working on SARS virus samples were infected “in two separate incidents,” according to the World Health Organization (WHO). The WIV collected virus samples from wild horseshoe bats and brought them to its lab for study in petri dishes, including whether they could infect human cells. The lab’s director insists the coronavirus that emerged in Wuhan doesn’t match any of its samples, but that would require an outside investigation to confirm.

The “Biosafety Level 4” lab, which first opened in 2015 and is a mark of nationalist pride for Beijing, did not handle deadly pathogens with adequate precautions. The Washington Post reported last month on 2018 State Department cables sounding the alarm about safety failures. WIV researchers themselves wrote in a 2019 article that “laboratory biosafety personnel training is relatively lacking,” according to the geopolitical consultancy Horizon Advisory.

Beijing reportedly ordered that other labs destroy test samples in the early weeks of the outbreak. And the WHO says China has declined to cooperate with an independent probe into the virus’s origins. When Australia proposed an independent investigation, Chinese officials threatened diplomatic and economic reprisals.