Police were called at 4.08am on Monday, 24 January to reports of a fire at a residential property on Railton Road.
Officers attended along with the London Fire Brigade and London Ambulance Service.
A 46-year-old woman was found unresponsive inside the property and later pronounced dead at the scene.
Following enquiries, the death is being treated as suspicious and officers from the Met’s Specialist Crime Command are investigating.
A 47-year-old man and a 17-year-old male were arrested on suspicion of murder on the evening of Wednesday, 26 January. They remain in custody.
Detective Chief Inspector Chris Wood, leading the investigation, said: “This is a tragic incident and my thoughts are with the woman’s family and friends as they come to terms with their loss.
“A dedicated team of investigators are working to establish the circumstances leading up to the fire and I am keen to hear from anyone who was in the area in the early hours of Monday and may have seen or heard anything suspicious.
“I recognise the impact this will have on the community and I would like to reassure the public that our enquiries so far have found nothing to suggest there is any wider risk.”
Anyone with information that could help the investigation is asked to call the major incident room on 020 8649 0424.
Alternatively, call 101 quoting CAD 724/24Jan or contact the independent charity Crimestoppers anonymously on 0800 555 111.