Police were called by the London Fire Brigade at 5.56am on Saturday, 6 March to reports of a fire at a residential property in Russett Way, SE13.
Three people, a 34-year-old woman and two boys aged five and 14, sustained injuries and were taken to south London hospitals.
Despite the best efforts of the emergency services and hospital staff, the five-year-old boy sadly died shortly before 8am
A post-mortem examination will be held in due course. Officers are not yet confirming the child’s identity.
The deceased and injured persons are all related to each other.
Detective Chief Inspector Laurence Smith is leading the investigation. He said: “We’ve worked extensively at the scene with the London Fire Brigade following this awful incident and can now confirm that the fire inside the address is thought to have been started deliberately. Other than the three occupants, we don’t believe there were any other persons present inside the address, and are ruling out the involvement of a third party.
“Wider family have been informed and our specialist officers are supporting them as they come to terms with their loss.
“What I need now is for any members of the public who might have information that could assist our investigation to make contact, so that we can increase our understanding of what has led to this tragic incident and provide the family with answers to the questions they are asking. No piece of information is too small – please call us immediately.”
The incident room can be reached on 0208 345 3985 with the reference Operation Tampere or CAD1321/06MAR. Alternatively call 101 or tweet @MetCC.
Information can also be provided to Crimestoppers, anonymously, by calling 0800 555 111.