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, has urged anyone who thinks they may own one of the appliances of the model FF175BP or FF175BG to call 0800 316 3826.
It 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.
Det Sup Fiona McCormack said she wanted to hear about anyone who was in the tower, whether or not they were meant to be in the building.
She said: “I do not want there to be any victims of this tragedy that we do not know about.
“Our priority is to understand who was in Grenfell Tower. We are not interested in people’s reasons for being in Grenfell Tower.”
She said she was concerned they did “not have the complete picture” and reassured people not to be nervous about contacting them.
“There may well be people who no one has contacted us about – who they know were in the building or have close links to Grenfell Tower.
“The Home Office has assured us that they are not interested in people’s immigration status and we are not interested in looking at that.
“What we are interested in is making sure that we know who is missing and we take every possible step to establish if they are safe and well.”
Some 250 specialist investigators have been deployed to find out what happened.
Police said the fire had not been started deliberately and the speed the fire spread was “unexpected”.
Det Sup 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.
“As we learn more, the scope and scale may well grow. We will look at the refurbishment. We are looking at the panelling and the entire facade of the building.”