By Hollie Silverman

Russian authorities told the World Health Organization (WHO) that "no case of plague has been recorded in Irkutsk," the agency said Tuesday, casting doubt about reports that anti-plague researcher Daria Shipilova died from suspected pneumonic plague.

The WHO statement comes as biosecurity experts question whether Russia's reported response to the incident was consistent with a routine plagueinvestigation. While there is no evidence that a biological weapon was involved, some experts say the scale of the reported response raises questions about whether officials were investigating a different infectious agent that has not been publicly identified.

Kevin Esvelt, an associate professor at the MIT Media Lab and a biosecurity researcher, cited reports that Russian authorities had deployed hazmat personnel and other containment measures.

"The obvious reason to lock down hospitals and deploy FSB agents and hazmat personnel, which Russia reportedly has done, is to contain a potentially transmissible biological agent before it spreads," Esvelt wrote on X. "The question is why they will not tell the world which one."