Health authorities in Siberia’s Irkutsk region have placed nearly 200 people under medical observation after a laboratory worker died from plague, according to media reports and a statement by a regional leader Friday.

Alexei Tsydenov, head of the neighboring republic of Buryatia, confirmed that the woman had died from an unspecified form of plague. Irkutsk officials had previously described the illness only as a “particularly dangerous infection.”

Citing information from Russia’s consumer safety watchdog Rospotrebnadzor and Buryatia’s government, Tsydenov said the woman had not visited his republic and that her infection was unrelated to the region.

“There are no plague outbreaks in the republic, including in areas bordering Mongolia,” he wrote on social media.

The woman was identified as Daria Sh., a 27- or 28-year-old employee of the Irkutsk anti-plague institute, by the exiled news outlet Lyudi Baikala (People of Baikal) and pro-Kremlin broadcaster REN TV.

She reportedly told medical staff that she had accidentally broken a test tube containing live bacteria while collecting samples for testing.

She was hospitalized Tuesday with symptoms of severe pneumonia in Shelekhov, a town near the regional capital of Irkutsk. She was placed on a ventilator and died Thursday, according to the reports.

The Shelekhov district hospital was placed under quarantine pending an assessment by a special commission.

At least 197 people who may have had contact with her were reportedly placed under medical isolation, including more than 100 in hospital wards.

Authorities canceled planned public events in Irkutsk, while law enforcement reportedly opened a criminal investigation into potential health safety violations resulting in death.

Irkutsk region Governor Igor Kobzev urged the public to remain calm after meeting with Rospotrebnadzor chief Anna Popova to coordinate emergency containment measures.

“All identified contact persons have been placed under medical observation. As of today, the contacts show no signs of illness, and their laboratory test results are negative,” Kobzev wrote on Telegram on Friday. He did not mention the reports of the laboratory worker’s death.

Media reports have described the suspected infection as pneumonic plague, which affects the lungs and can spread between humans through respiratory droplets. Tsydenov’s statement did not specify the form of plague.