Homes were evacuated after two neighbouring four-storey town houses collapsed in west London.
Emergency services were called to Durham Place in Chelsea at 23:35 GMT on Monday where the buildings, which were being redeveloped, had fallen in.
A 25m (82ft) cordon was put in place and about 40 people were told to leave nearby properties while drone teams and police dogs searched the rubble.
No injuries have been reported, London Fire Brigade said.
Station Commander Jason Jones said there had been “a total collapse of the buildings from the roof to ground level”.
He added: “Nobody is thought to have been inside the building at the time of the collapse.”
The Met Police said those living in nearby houses had been evacuated “as a precaution”.
Local roads remain closed and police cordons are still in place.
The collapsed buildings form part of a terrace of houses which were built in the late 1700s opposite land owned by the Royal Hospital Chelsea – the home of the Chelsea Pensioners.
A seven-bedroom house in the block sold for £16m last year, according to property website Rightmove.