India, Oct. 7 -- The World Health Organization is seeking more information from Russia after a laboratory worker at the Irkutsk Anti-Plague Research Institute died of severe pneumonia on October 2. The death raised concerns about a possible case of pneumonic plague linked to a laboratory exposure. Russian authorities have rejected those reports and said the cause of the illness remains undetermined.

A 28-year-old laboratory technician, identified in Russian media as Darya Shipilova, was hospitalized around September 29 with severe pneumonia and died on October 2.

She worked at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East, which studies plague and other high-risk pathogens.

Authorities placed dozens of people w...