India, Oct. 6 -- A laboratory worker at a Siberian institute specialising in plague research fell ill and later died under undisclosed circumstances, prompting authorities to place dozens of people under quarantine, while Russia's health watchdog chief travelled to the Irkutsk region.

Amid reports of the death, Russian authorities sought to downplay concerns over reported possibility of "pneumonic plague" behind the worker's death as Kremlin spokesman Dmitry Peskov said that people should "rely on Rospotrebnadzor's official statements rather than... rumours and speculations".

Rospotrebnadzor is Russia's consumer and health watchdog.

The reports emerged on Friday stating that 28-year-old Darya Shipilova had died from suspected pneumonic...