India, Oct. 5 -- Russian authorities have quarantined a hospital and are monitoring people who came into contact with an employee of a plague research institute in Siberia who contracted pneumonia of an "unknown" cause. Local state TV reported that the woman died last week.

Russian authorities said they found no evidence that her illness was caused by any of the pathogens she worked with. But the case has raised concern in Russia after unconfirmed media reports suggested she may have died from pneumonic plague - a less common but severe form of plague that can spread from person to person.

The woman worked at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East in Irkutsk, southeastern Siberia. A state TV station in Ir...