The house fire that left two women and three children dead was "severe", a spokesman for South Yorkshire Fire and Rescue said.
He said: "Our investigators are arriving here at 9am, so we we will know more later on this morning."
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United in grief, the people of Manchester have come together in defiance to the suicide bomber who killed 22 people on Monday evening.
Hashem Abedi, who was held in Tripoli on the same day his father was arrested, was planning terror in the Libyan city, officials have said.
A notably mild night, feeling close and stuffy.