A Nottingham house which was damaged by a gas explosion, badly injuring both occupants, had recently had a new boiler fitted, it has been confirmed.
The property in Stockhill Lane, Stockhill, was wrecked by the blast on Sunday night.
A woman in her 40s and a man in his late 30s are in a critical condition in hospital.
Nottingham City Homes, which manages the house, said a new boiler was installed six weeks ago.
The explosion was heard up to half a mile away and caused part of the house's rear wall to collapse and much of the first floor to give way.
Nottingham City Homes, which manages about 29,000 properties in the city, said it had been carrying out renovations at the house.
A spokesman added that it would be working with other agencies to discover what had caused the blast.
Nottinghamshire police said they would wait until structural engineers had declared the building safe before an investigation could fully begin.
Chf Insp Rob Griffin said they were keeping an open mind about what had happened.
"Structural engineers have told us today that it is just not safe to go in there and until it is deemed safe to go in there, then we won't.
"And really the true secret to what has gone off here probably lies within those four walls.
"We want to get in there quickly but we are not going to risk anybody's welfare by going in there."