Detective Sergeant David Speight says whoever caused the fires may have flash burns on their body.
Michael and Angela Broderick, who are both deaf, had a narrow escape when an arsonist destroyed their home in Burbage in Leicestershire.
Police are appealing for the public to contact them if they have any information.
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Largely fine and hot but with isolated thunderstorms.
Cooler with thundery showers.
The parents of a 17-year-old who died in a flat fire at Langley Mill have paid tribute to “an incredible son and brother.”