A woman and four young children have died and one other child is in hospital after a house fire in Essex in England.
Essex Police are working to establish a possible motive for the suspected arson attack in Harlow.
Police and fire crews were called to the Barn Mead estate at 1.45am, at which point flames were coming from the front and back doors.
Dr Sabah Usmani, and her sons Sohaib, 11, Rayan, six, and her 13-year-old daughter Hira, died in their end-of-terrace house.
A third son, Muneeb, nine, and daughter Maheen, three, were rescued by fire crews and taken to hospital. However, the boy died of his injuries in the Princess Alexandra Hospital.
The children's father, Dr Abdul Shakoor, suffered minor injuries in the blaze and is said to have "fought hard" to save his family.
Police said he is not being treated as a suspect.
Witness reports suggest between one and four people were in the area at the time and police said such sightings will form key lines of inquiry.
A car was also found alight a short distance from the house.
That vehicle was not connected to the family, but the fire is also being treated as arson.
Harlow area commander Superintendent Luke Collason said racism was not a problem in the neighbourhood and police have not had any previous contact with the family.
Dr Shakoor works at the Princess Alexandra Hospital and Dr Usmani did not work as she cared for the children.
Originally from Karachi, Pakistan, they had lived in Saudi Arabia, where the children were born, for more than a decade before moving to the UK.
A possible line of inquiry is that the family were not the intended target of the attackers.