A 17-year-old boy is in a serious condition in hospital after an arson attack in West Yorkshire.
Emergency services were called to a house on Stonedene Court, Heckmondwike, Kirklees, at about 04:10 BST.
Four people in the house managed to escape the fire by jumping from upstairs windows, with the teenage boy suffering burns and an injury from jumping.
West Yorkshire Police said the attack was being treated as attempted murder.
The 17-year-old’s condition is described as serious but stable.
A woman and two girls, aged 16 and 11, needed treatment for the effects of breathing in smoke.
Police said the attack was “very serious” and could easily have been fatal for the family.
Det Supt Mark Swift said: “This is clearly a very serious incident in which a male has suffered burn injuries and three females have also suffered smoke inhalation.
“It took place at a time of night when a family were at home sleeping and could quite easily have had fatal consequences for those inside.
“We are treating this incident as an attempted murder and I am appealing to members of the public for information.”
Det Supt Swift said it was likely the attackers were also injured and anyone with information – particularly about men or boys buying petrol in cans from garages – should call 101.
“It is quite possible the suspects will have suffered some injuries as a result of lighting the fire and I would like to speak to anyone who has information about males having turned up at home this morning with burns,” he said.
Police also want to hear from anyone who saw suspicious behaviour, or who has CCTV images of the area.