Cladding and insulation used in at least 60 tower blocks has failed a new fire safety test, the BBC understands.
The test was more thorough than previous checks after the Grenfell Tower fire, which just examined cladding from high-rise buildings.
The new test checked the cladding in combination with the foam insulation that was used in Grenfell.
That combination is used in at least 60 other blocks. Only nine – in Salford – have been indentified so far.
The Department for Communities and Local Government will publish its full findings of the “whole system fire test”, along with guidance, later this morning.
At least 80 people died in the Grenfell Tower fire in North Kensington on 14 June.
On Thursday, BBC Newsnight reported that the test – conducted by the Building Research Establishment near Watford – involved starting a fire underneath a large-scale mock-up of the insulation system used at Grenfell
The mock-up used a so-called PIR plastic foam, a type of combustible insulation, and aluminium panels with a combustible polyethylene plastic core.
This is the most flammable of the six combinations of insulation and cladding that will be tested.
Salford Council had already said it expected its towers to fail.
The nine blocks built in the 1960s were re-clad recently with shiny coloured panels, and insulation to cut energy bills.
Salford had already begun removing cladding and the process will continue.
It is likely to cost the authority tens of millions of pounds and they are asking for help from central government.
The test results come after police investigating the Grenfell Tower fire told residents they have “reasonable grounds” to suspect that corporate manslaughter offences may have been committed by Kensington and Chelsea Council and the tenant management organisation that ran the block .
Senior executives are likely to be interviewed under caution.
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Meanwhile, the site manager at Grenfell Tower, Michael Lockwood, has told a public meeting the building would be covered in a protective wrap in August.
He said that he expected the demolition of the tower block would begin “towards the end of 2018”.