A number of high rises across England are using similar cladding to Grenfell Tower, says the government.
Tower blocks across the UK are being examined after the London blaze, which left 79 people dead or missing, presumed dead.
Eleven residential high-rise buildings in eight local authority areas have been found to be covered in combustible cladding following safety tests.
And the BBC is reporting that Premier Inn is "extremely concerned" about cladding on three of its hotels in Maidenhead, Brentford and Tottenham, which did not appear to comply with government guidance for tall buildings - although it did appear to be a less flammable type than that used at Grenfell Tower.
Cladding is thought to have contributed to the rapid spread of fire at Grenfell Tower. In a statement to the House of Commons yesterday, Theresa May said some of the results had already come back showing that the cladding used was flammable. All local authorities responsible for the flats have been informed.
Mrs May said the councils were working with local fire services and "taking all possible steps to ensure buildings are safe and inform affected residents."
Councils were told to give details to the government about the cladding they used in the tower blocks by Monday.
The Department for Communities and Local Government is co-ordinating tests on it - with up to 100 able to take place in a day. A communities department spokesman said: "The situation is that 600 buildings have cladding. It is not similar, it is all types of cladding.
"Of these 600, we want landlords to check if they have aluminium composite material (ACM) cladding. Of those 600, some of those would have ACM; we want to test them to see if they have ACM."
This clarifies an earlier briefing by Downing Street that initially suggested 600 tower blocks had "similar cladding" to Grenfell Tower.
Meanwhile, the chief executive of west London's Kensington and Chelsea Council - who's been among the officials and politicians facing criticism over the Grenfell Tower fire - has resigned. Nicholas Holgate called the disaster, in which at least 79 people died, "heart-breaking", adding that remaining in office would be a "distraction".
He also said that Local Government Secretary Sajid Javid had asked him to quit, but Mr Javid hasn't yet commented on the claim.
Prime Minister Theresa May announced on Wednesday that 68 social housing flats in Kensington Row, about 1.5 miles away from Grenfell Tower, would be made available to survivors.
In response to the Prime Minister’s statement on the Grenfell Tower fire, David Orr, Chief Executive at the National Housing Federation, said: “Since the tragic fire that took place last Wednesday at Grenfell Tower, housing associations across the country have worked tirelessly to reassure tenants, carry out additional safety checks and, in London, offer support to the Royal Borough of Kensington & Chelsea.
“Right now, housing associations are working closely with DCLG to identify and test any tower blocks with ACM (aluminium composite material) cladding. And, while the cause of the fire and its spread remains unconfirmed, housing associations will be scrupulous in carrying out other fire safety checks for example on sprinklers, smoke control systems and emergency procedures.
“We want to reassure residents of these blocks that testing on your building does not necessarily mean that it is unsafe, and in instances where cladding is found to be combustible, action will be taken.
“As always, the sector’s first priority is its residents. We will work in partnership with local authorities and fire services across the country to ensure people in tower blocks are safe and secure."
