Police have said that the home where a mother and her five children were killed by a fire was burgled on the night of the tragedy.
Sabah Usmani, her sons Sohaib, 11, and Rayyan, six, and daughter Hira, 13, died in Barn Mead, Harlow, Essex, on October 15. A third son, Muneeb, nine, and daughter Maheen, three, died later in hospital.
Essex Police now say they believe there was a burglary at the property on the night of the fire in which a laptop belonging to the children's father and the only member of the family to survive the fire, Abdul Shakoor, was stolen.
Detective Superintendent Rob Vinson said he wants to speak to a teenage boy and young girl who were seen throwing a laptop bag away near the family home.
Officers originally said they suspected the fire was an arson attack but later claimed no accelerant had been found at the scene. Police have now confirmed scientists found no evidence of a flammable liquid being used.
Mr Vinson, the senior investigating officer on the case, said: "Recent developments have moved the investigation forward in a number of directions and we now believe that there was a burglary at Dr Shakoor's house in Barn Mead in which items were removed from the house. We believe that this burglary took place after the family had gone to bed and before the fire was discovered.
"Our inquiries have revealed that in Harlow during the same evening and early morning there were two other unsuccessful attempts to break in to other properties and one where entry was gained but the suspect was disturbed and nothing was taken. How these incidents relate to the current investigation is ongoing."
The officer said he was keen to speak to a teenage boy of around 15 or 16 wearing a tracksuit, and a slim girl in a school uniform who were seen throwing Dr Shakoor's laptop bag away near garages in Whitewaits, Harlow. The bag was found near the garages on October 26 containing personal papers and a laptop lead.
"We urgently need to speak to these two young people about where they found the bag," Det Supt Vinson said.
He appealed to the public for help in finding Dr Shakoor's black laptop, which was bought in Saudi Arabia and had a two pin lead that was used with an adaptor. He said: "Dr Shakoor remembers leaving his Toshiba Satellite laptop in the lounge when he went to bed that evening. The fire that raged through the downstairs of the house has left the contents totally destroyed. We now believe that this laptop may have been stolen."