This was reported by the press service of the Investigative Committee.
It is noted that the 70-year-old owner of the apartment was hospitalized.
The investigators found that he lived alone and was registered with a narcologist.
"In 2010, he refused to provide gas supply services, and a metal plug was installed on the gas pipeline that goes to the gas stove," the department noted.
Investigators are considering several versions of what happened.
According to the investigation, cotton could have occurred due to poor quality gas supply services or careless actions related to improper operation of gas equipment.
The number of victims of the explosion in a residential building in Naberezhnye Chelny increased to five.
One of the victims died in the hospital.