A man, a woman and their two children were injured after they jumped off the roof of the residential building they lived in, attempting to escape the flames that had enveloped their Sofia flat on Friday.
The woman died in hospital shortly after the accident, doctors reported.
The condition of her husband, 45, remains critical. The two children, aged 7 and 11, were hospitalized with serious injuries but their lives are not in danger.
In panic, the family tried to jump off the roof to the top of a neighboring building.
The fire, which triggered the desperate actions, broke after a gas boiler exploded in the apartment, located in a building in Sofia's central Pirotska Street.
Fire brigades managed to extinguish the blazes after several-hour fight.
The firefighters searched for more people, who could probably left in the burning six-storeyed building after the fire broke but fortunately have not found anyone.