Sen. Rand Paul, R-Ky., is raising concerns about whether Russia could be conducting biological weapons research involving the plague after a worker at an anti-plague research facility in Siberia died following a severe case of pneumonia.

Paul, who chairs the Senate Homeland Security and Governmental Affairs Committee, said Tuesday that Russia's history of biological weapons research and the unusual circumstances surrounding the worker's death warrant closer examination.

"We do know from defectors in the 1970s and '80s that they were weaponizing the plague," Paul said in an interview with Fox News host Will Cain. "So, this is concerning."

The senator did not present evidence that the worker's death was connected to a biological weapons program, nor did he claim to have confirmed that plague was responsible for the death. Instead, Paul said U.S. officials should examine satellite imagery and Russian military activity for signs of unusual activity.

The case involves Daria Shipilova, a 28-year-old employee at an anti-plague research facility in Russia's Irkutsk region. She reportedly became seriously ill after breaking a test tube containing live bacteria on Sept. 25 and later died after being hospitalized.

Irkutsk region Governor Igor Kobzev described the cause of death as "pneumonia of unknown etiology," meaning the specific cause had not been determined. Authorities subsequently investigated the incident and isolated nearly 200 people who may have been exposed.

The unusual circumstances have also drawn the attention of international health officials. The World Health Organization has sought additional information from Russian authorities about the death and a potential second incident.

Paul said Russia's lack of clarity surrounding the case was "alarming," arguing that authorities should be able to determine relatively quickly whether the plague was responsible for the worker's death.

The Centers for Disease Control and Prevention has acknowledged the incident and said it is closely monitoring reports of a suspected case of pneumonic plague. The agency said there is currently no indication of a broader threat to the United States.

Pneumonic plague can spread between people through respiratory droplets during close contact, making rapid identification, treatment and monitoring of potentially exposed individuals important public health measures.

While there is currently no confirmed evidence that the incident involved a biological weapons program, Paul's comments are adding pressure for greater transparency as Russian authorities investigate the unexplained death and international health officials seek more information.