A reward of up to £10,000 is being offered following a house fire which killed six members of the same family.
Sabah Usmani, her sons Muneeb, nine, and Rayyan, six, and daughter Hira, 12, died in the blaze in the early hours of October 15 at their home in Barn Mead, Harlow, Essex. A third son, Sohaib, 11, and daughter Maheen, three, died later in hospital.
Dr Usmani's husband, Abdul Shakoor, was the only survivor.
Essex Police recently said they suspect there was a burglary at the house shortly before the fire.
Crimestoppers has now said it will pay the reward for information leading to the arrest and conviction of those responsible.
Ann Scott, the charity's eastern regional manager, said: "This is an absolutely heartbreaking incident which has devastated and shocked the entire community.
"It is impossible to imagine how Dr Shakoor, who survived the fire, is coping with the loss of his family.
"Please come forward to the independent charity Crimestoppers so this truly awful crime can be solved."
She added that people had "nothing to fear" by contacting Crimestoppers as all witnesses could remain anonymous.
Information is particularly wanted about a group of four males who were outside the house in the early hours of October 15. They are described as aged between 16 and 19 and were wearing tracksuits and baseball caps.