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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The Labour former cabinet minister was in the chamber for a backbench debate led by Labour MP Sarah Jones, who used to work for Lady Jowell.
A police officer narrowly escaped injury and possibly even death after a house exploded just yards in front of him.
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