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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Some sunshine on Sunday, with possible afternoon showers.
Magician Richard Jones has won Britain's Got Talent 2016 after wowing the public with his amazing magic acts.
Tonight it's the band's turn to have a party as they celebrate the Foxes Premier League success with a homecoming gig in their stadium.