(CNN) - Authorities in Russia are investigating after a woman who worked at a plague research institute died following a suspected laboratory accident.

A 28-year-old woman has died after a suspected lab accident at the Anti-Plague Research Institute in Siberia, Russian authorities say. She was diagnosed with pneumonia of “unknown” origin before her death.

Authorities are now investigating whether a dangerous infection, such as pneumonic plague, may have been released. They say the situation is stable at this time.

The U.S. Centers for Disease Control and Prevention is monitoring the incident.

“We are monitoring the situation closely with the CDC and our other interagency partners,” a U.S. State Department spokesperson told CNN. “Many details have not been confirmed. We encourage Russian authorities to share accurate information quickly and openly.”

What is pneumonic plague?

Pneumonic plague is one of three types of plague caused by the bacterium Yersinia pestis. It is the only type of the disease that can be spread from person to person through infectious droplets coughed out by an affected patient, according to the CDC.

Symptoms of pneumonic plague include fever, headache, weakness and rapidly developing pneumonia.

The CDC says that while the plague is a potentially life-threatening disease, it is treatable with antibiotics.

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