The Grenfell Tower fire in London started in a fridge freezer, and outside cladding failed safety tests, police say.
Insulation on the building also failed tests and the Metropolitan Police will consider manslaughter charges.
Seventy-nine people are feared dead after the blaze destroyed 151 homes in the Kensington tower block.
The government has ordered immediate testing of the Hotpoint fridge freezer which was involved.
Whirlpool, who owns Hotpoint, said: “We offer our most profound condolences to the victims, those who have lost loved ones, homes, and possessions, and to their friends and families.”
It said it was working with the authorities to obtain access to the appliance so that it could assist with the ongoing investigations.
Police said the fire had not been started deliberately and the speed with which the fire spread was “unexpected”.
All criminal charges are being considered “from manslaughter onwards” including health and safety and, fire offences.
Every company involved in the building and refurbishment of Grenfell Tower will also be looked at as part of the investigation.
Det Sup Fiona McCormack said police had been in the tower “from top to bottom”, adding that next week a lift would be installed to the outside of the building.
But she did say the forensic search “may not be complete until the end of the year”.
“There is a terrible reality that we may not find or identify everyone who died due to the intense heat.”
Preliminary tests on the samples of insulation showed it burned soon after the test started, and more quickly than the cladding tiles.
However, they both failed the police’s safety tests – which are similar to those being carried out by the UK government.
The cladding, insulation, fixings and installation will be examined both individually and how they worked together.
“The investigation will be exhaustive,” said Det Sup McCormack. -BBC
