A woman and her four daughters who were killed when their house in Lancashire was deliberately set alight died from smoke inhalation, detectives have said.
Mrs Riaz and her daughters died in their beds from smoke inhalation
Post-mortem examinations have been carried out on the bodies of Caneze Riaz, 39, and Sayrah, 16, Sophia, 15, Alicia, 10, and Hannah, three.
All five were already dead in bed when fire crews broke into their Accrington home in the early hours of Wednesday.
Mrs Riaz's husband, Mohammed, remains in a critical condition in hospital.
He was brought out from the house and resuscitated by firefighters at the scene. Mr Riaz is being treated in a specialist burns unit at Wythenshawe Hospital in Manchester.
Detectives want to speak to him as part of the murder inquiry and are waiting at his bedside.
Investigations into the fire, which was started shortly before 0200 GMT, have revealed that the house in Tremellen Street had been locked up from the inside and flammable materials used in the fire.
Forensic examinations have deduced that whoever set the fire did not leave the house afterwards.
The couple's fifth child, 17-year-old son Adam, was in hospital receiving treatment for leukaemia when the blaze started.
Police have broken the news that his mother and sisters are dead.
Special assemblies have been held at Hyndburn Park Primary School, where Alicia was a pupil, and at Accrington Moorhead Sports College where her two elder sisters studied.
Andrew Bateman, head teacher at Accrington Moorhead Sports College, said: "We held a full school assembly this morning.
"Everyone came together, 1,000 staff and pupils, to share their grief together. It was very calm and quiet."
As well as the assembly, the college has been providing individual and group support to help students try to come to terms with the tragedy.
Mr Bateman added: "Pupils have also had a time of reflection in their classes to discuss with teachers what has happened.
"Sayrah and Sophia were pupils here. Their close friends are quite distraught and are finding it hard to come to terms with it all."
Mourners have laid dozens of floral tributes outside the house where the four girls and their mother lost their lives.