A 28-year-old employee at Russia’s Irkutsk Anti-Plague Research Institute died after developing an unexplained form of pneumonia, CNN reported, prompting precautionary measures and renewed attention from health officials.

Russian authorities said tests did not detect microorganisms linked to the woman’s work at the institute. Even so, people who may have had contact with her were isolated while officials continued examining the circumstances surrounding her illness and death.

The case has also drawn attention in Washington. President Donald Trump said U.S. intelligence officials were discussing the situation and that he planned to speak with Russian President Vladimir Putin, according to CNN.

The State Department has called for clear and timely information from Russian authorities. The World Health Organization has also been in contact with officials in Russia and has assessed the broader public health risk as low.

No plague outbreak has been confirmed, and authorities have not established that plague caused the woman’s death.