A flat fire that killed a young boy was started deliberately, according to Metropolitan Police detectives.
The five-year-old died in hospital following the blaze in Lewisham, south London, on Saturday.
Two people related to the child, a 34-year-old woman and a 14-year-old boy, were also taken to hospital.
Detective Chief Inspector Laurence Smith, who is leading the investigation, 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.”
Anyone with information can call police on 0208 345 3985, citing reference Operation Tampere or CAD1321/06MAR, or Crimestoppers anonymously on 0800 555 111.
Police were called to the blaze in Russett Way by firefighters shortly before 6am on Saturday, and the boy died in hospital some two hours later.
Officers did not identify the victim. A post-mortem examination will be conducted “in due course”, a statement said.