It completely destroyed the staircase and ceilings on the first three stories. A total of 21 rescuers were working at the scene. City Mayor Vladimir Afanasenkov told RIA Novosti that 11 people had been given medical aid, and that one was being treated in hospital. Police said liquefied petroleum gas cylinders may have detonated in the building.
''Residents of the building were secretly using liquefied gas,'' the spokesman said. Several cylinders have been found in the debris, he added.
Forensic experts were working at the scene to establish the cause of the explosion.