Russia's consumer protection watchdog Rospotrebnadzor has denied that an employee of an Irkutsk anti-plague institute died of plague, saying she had pneumonia of undetermined origin, Kursiv Media reported on October 4.

The denial follows days of unconfirmed reports of a plague death in Shelekhov, an industrial town of 40,262 people in Irkutsk region that is home to the Irkutsk Aluminium Plant. On October 3, nearly 200 people were placed under medical observation after the reported death, and the official line now contradicts the earlier accounts.

Rospotrebnadzor named the woman as Darya Shpilova, 28, who worked at the Irkutsk Anti-Plague Institute of Siberia and the Far East. She was hospitalised on September 29 and died on October 1, local media reported.

A commission found that no accidents involving pathogenic microorganisms had occurred at the institute and that no staff members had symptoms of an infectious disease.

Investigators examined two theories, a trip to Thailand and a laboratory accident involving a broken test tube containing the plague pathogen, and found no evidence for either. The watchdog said the epidemiological situation in the region remained stable.

At least 197 people had contact with the deceased patient, regional news site Krasnodarmedia reported, citing Izvestiya. Of these, 189 were hospitalised for observation, 114 in one regional hospital, 63 in another and 12 at the anti-plague institute. Eight were not hospitalised. All showed no signs of illness and their laboratory results were negative.

Shelekhov district hospital closed its inpatient ward on the evening of October 1 over a suspected dangerous infection in a deceased patient, regional news site Stolitsa na Onego reported.

Irkutsk Governor Igor Kobzev convened an emergency meeting of the regional sanitary and epidemiological commission with Russia's chief state sanitary doctor Anna Popova, and Rospotrebnadzor approved an operational action plan, Krasnodarmedia reported. Local authorities asked residents to limit visits to Shelekhov and neighbouring towns, and a city clean-up planned in Irkutsk on October 3 was postponed for safety reasons.

The Irkutsk Aluminium Plant, which has 2,154 employees, introduced mandatory masks. Plant director Artyom Fominykh announced the move on Telegram.

"We have introduced a mask protocol at the facility as a precaution. God protects the cautious, so follow safety measures. If symptoms appear, seek medical help immediately," Fominykh said, Stolitsa na Onego reported. He added that Rospotrebnadzor was carrying out the necessary procedures and that identified contacts showed no signs of illness.

Gennady Onishchenko, an epidemiologist and academician of the Russian Academy of Sciences, said the infection was "likely not plague", while noting that specialists have treatment and prevention protocols if it is confirmed, Krasnodarmedia reported.

Uzbekistan strengthened sanitary controls at its borders after the incident with no plague cases have been confirmed in the country.