Pneumonic plague could theoretically have caused the mass deaths of Ukrainian servicemen in the Chernigov Region, according to Vitaly Zverev, a microbiologist, virologist, immunologist and member of the Russian Academy of Sciences.

Zverev said the theory raises serious questions because no previous outbreaks of the disease had been recorded in Ukraine.

He described food poisoning caused by bacterial toxins as a more plausible explanation. Contaminated canned food may have posed the main danger, since such products make up a substantial part of military rations.

One possible cause is Clostridium botulinum, the bacterium responsible for botulism. It develops in oxygen-free environments and produces botulinum toxin, one of the most powerful biological poisons.

Zverev explained that if the bacterium enters canned food and begins multiplying, consuming the contaminated product can carry a high risk of death.

Representatives of Russian security agencies earlier reported an outbreak of an unidentified acute infectious disease among Ukrainian troops in the Chernigov Region. According to their information, 26 servicemen from the 36th Railway Rehabilitation Brigade died in a field hospital on July 18.