An 11-year-old boy died following an explosion at a house in Bulgaria's northern town of Sevlievo on Saturday.

The explosion occurred at around 10.30 pm.

The boy's older sister was wounded in the accident. The 15-year-old girl was taken to hospital where she underwent surgery. The girl is not in a life-threatening condition, according to reports of Darik radio.

The children were living alone and their parents were working in Belgium, according to the press office of the Sevlievo Municipality.

The cause of the blast has not been identified. The house was not equipped with natural gas heating, and the bathroom water heater was fit. The police officers found an empty gas cylinder during the search of the remnants of the building.

The one-story house was razed to the ground and the nearby buildings were damaged by the blast.

The Sevlievo Municipality is looking for relatives of the family to accommodate the 15-year-old girl after she is released from hospital.

The Sevlievo Municipality is also trying to contact the parents of the two children.