Authorities reported on Friday that 28-year-old Darya Shipilova, a lab tech at a research facility in Siberia, had died at the Shelekhov Hospital in a suspected case of the plague, according to The Moscow Times.

She had been hospitalized with acute pneumonia symptoms on Tuesday and was placed on a ventilator, with reports saying she died two days later on Thursday.

The incident prompted Shelekhov Hospital to quarantine, soon followed by several others in the Irkutsk region, even as health authorities reassured residents everything was fine, the outlet reported. The Irkutsk Aluminum Smelter in Shelekhov also instituted a mask mandate for “preventative measures,” according to its director, Artem Fominykh.

On Saturday morning, the local government for the town of Baykalsk advised residents to avoid traveling to Shelekhov and other nearby towns because of a plague-related death, but the post was taken down shortly after, according to the Times

People of Baikal reported that Shipilova had been exposed to the disease after she had accidentally broken a test tube containing live bacteria on Sept. 25. She first developed symptoms during a work expedition near the Russian border with Mongolia, according to the outlet.

However, Russian epidemiologist Mikhail Favorov, who now lives in the U.S., alleged that the broken test tube story is a government cover-up.

“It’s laughable,” Favorov said, according to the Post. “Someone working at the anti-plague Institute in Irkutsk wears a protective anti-plague suit. If you break a test tube, the likelihood of infection is actually very low. In short, it doesn’t matter to the general public — they’ll believe the ‘dropped test tube story.’”