Russia is investigating the death of a 28-year-old laboratory worker at a plague research institute in Siberia, with global health authorities pressing Moscow for more information amid concerns over a possible pneumonic plague case.

The worker, identified in Russian media as Darya Shipilova, died on Friday after developing pneumonia of undetermined origin at the Anti-Plague Institute of Siberia and the Far East in Irkutsk. Russian health regulator Rospotrebnadzor said on Wednesday that nearly 5,000 tests found no dangerous pathogens and that 90% of the 200 people initially placed under observation had been released, insisting there was no epidemic risk. The agency added that Shipilova had been vaccinated against plague, making her "immune to the dangerous infections with which she worked" .

World Health Organization Director-General Tedros Adhanom Ghebreyesus said the UN agency lacks a "full picture" of the event and has requested clarification on media reports of a second employee with pneumonia of undetermined cause. "We don’t yet have the full picture of this event," Tedros said, urging Russia to provide "timely, complete and transparent information" to assess public health risks .

U.S. President Donald Trump told reporters on Wednesday that he does not believe the death is linked to a bioweapon, adding that Russia claims the situation is "very much under control." Trump said he had set up a call with Russian President Vladimir Putin, though Kremlin spokesman Dmitry Peskov denied any call had been scheduled. The U.S. State Department has formally requested additional information from Russia, while the EU has also called for transparent reporting .

Russian authorities have dismissed media reports of a second suspected case as "false information," with Peskov directing inquiries to official statements from Rospotrebnadzor .