23 psychiatric patients, most of them elderly, died when a fire swept through their care facility in southern Russia on Saturday night, which is the latest incident to hit mental health hospitals in the country.
Russian emergency services reported that 51 people were rescued while 23 others were hospitalised.
"The bodies of 23 people have been found during an on-site inspection," the investigative committee said in a statement on Sunday.
70 patients and four nurses were in the hospital when the fire broke out just before midnight (2100GMT) Saturday at the psychiatric hospital in the village of Alferovka, located in Voronezh region, about 600 kilometers (350 miles) south of Moscow.
According to a list of patients released by the Russian Emergencies Ministry, most of those who died in the fire were in their 60s and 70s, as some were in their 40s and 50s.
A Russian local media reported that those who died were bedridden patients who had been given tranquilizers.
"They simply did not wake up," AFP reported from the scene.
More than 440 firefighters and emergency workers spent about three hours to bring the fire under control. Investigators have not yet determined the cause of the fire. The investigative committee said that it opened a criminal probe into the deaths, suspecting of negligence.
The fire was the latest incident to hit a psychiatric facility in Russia, where officials often take a lax approach to safety measures for fire.
A great number of people die also in house fires each year in the country.
In September 2013, a fire at a psychiatric hospital in northwest Russia killed 37 people, as within the same year, another blaze in a psychiatric ward near Moscow killed 38 in April.