The Grenfell Tower fire started in a faulty fridge and the cladding and insulation on the block has failed safety tests, police said.
Metropolitan Detective Superintendent Fiona McCormack said the Hotpoint FF175BP model had not been subject to any product recall.
Witnesses at the scene of the 24-storey blaze in north Kensington on June 14 described hearing one resident claiming it was his appliance which was responsible.
— Metropolitan Police (@metpoliceuk) June 23, 2017
The number of people to have died, including those classed as missing presumed dead, remains at 79, she said.
Ms McCormack said the tests carried out as part of the investigation were “small scale”, but added: “All I can say at the moment is they (tiles and insulation) don’t pass any safety tests.
“What we are being told at the moment by the Building Research Establishment is that the cladding and insulation failed all safety tests.”
She added: “Our investigation is to establish how the fire started.”