The victim, named locally as Juanita Tuckey, 82, suffered burns to her hands and arms as a result of the blast at the house in Whitecraig, East Lothian.
The pensioner, who neighbours said was originally from Spain, was taken to Edinburgh Royal Infirmary yesterday afternoon. Fire crews switched off gas and electricity supplies during checks to the house.
One neighbour said: "It was a very loud but strange noise. It was as if something fell off the back of a lorry.
"Ms Tuckey lives on her own so I hope she's okay."
The bungalow is semi-detached and the roof is bowed in the middle with many tiles missing or fallen to the ground.
Crews were last night working to secure the council property so an investigation into the cause of the blast can take place.
Frank Fairgrieve, principal surveyor at East Lothian Council's building standards department, said: "We don't know how long it will be until we can determine what happened.
"We need to secure a perimeter then let the demolition workers enter to secure the roof."