WASHINGTON (Diya TV) — The United States is monitoring reports of a suspected pneumonic plague case in Siberia after a laboratory worker died and Russian authorities imposed quarantine measures. Russian officials have not confirmed a plague infection.

Secretary of State Marco Rubio said Monday that Washington was following developments closely.

“I don’t think it’s cause for alarm, but it is cause for focus,” Rubio said. The State Department said it was monitoring the situation with the Centers for Disease Control and Prevention and urged Russia to share accurate information promptly.

Local reports identified the worker as Darya Shipilova, a laboratory technician at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East. She entered a hospital in nearby Shelekhov in late September and died early Friday.

Russia’s public health agency, Rospotrebnadzor, described her illness as pneumonia of unknown origin. It said extensive testing found no microorganisms associated with her work and that investigators had uncovered no incident involving pathogens at the institute.

Authorities nevertheless quarantined the Shelekhov hospital, suspending inpatient admissions and discharges while keeping its outpatient clinic open. Regional officials said they were monitoring people who had contact with the worker.

RFE/RL reported that institute employees remained inside the facility while awaiting test results. Independent local media also reported a possible laboratory accident, but Russian authorities have not confirmed that account.

On Monday, Irkutsk Gov. Igor Kobzev described the regional health situation as stable and said no additional institute employees had sought medical care in recent days.

Pneumonic plague infects the lungs and can spread between people through respiratory particles, according to the World Health Organization. The disease can progress rapidly, but early antibiotic treatment can save lives. Laboratory testing must confirm a diagnosis.