Assistant Chief Constable Steve Cotterill said "please do not see these two arrests as the police inquiry coming to an end" and appealed to the public for additional information.
He said: "I need additional information from the public out there to really get to the truth to what was the reason behind that fire - whilst I know the cause I do not know the reason behind it and I'm still anxious for that information to come forward."
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At least 27 high-rise blocks of flats in 15 local authority areas have failed fire cladding safety tests, the Government has announced.
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The company said its role was not to decide what was or was not compliant with local building regulations.