Police have revealed that five of the six children who died in a house fire were killed by smoke inhalation.
Derbyshire Police said the results of post-mortem examinations revealed that Jade Philpott, 10, and brothers John, nine, Jack, seven, Jessie, six, and five-year-old Jayden breathed in smoke when fire ripped through their home in Allenton in the early hours of Friday.
The blaze also claimed the life of their 13-year-old brother Duwayne, who died overnight in the Birmingham Children's Hospital with his parents at his bedside. A Derbyshire Police spokeswoman said a post-mortem examination has yet to be scheduled for Duwayne and detectives are keeping an "open mind" as to how the fire started.
A 28-year-old woman and 38-year-old man, both from Derby, were arrested by officers investigating the deaths but were released without charge. Police said they were still treating the fire as suspicious.
The children were asleep in their beds upstairs when the fire broke out at the semi-detached house in the early hours of the morning. The children's father, Mick Philpott, made a "valiant" attempt to save them, police said.
Assistant Chief Constable Steve Cotterill said: "This investigation is still at an early stage and it should be stressed that we have not yet had the opportunity to speak to Mr and Mrs Philpott properly because they've been caring for their son in Birmingham.
"I want to thank the local community who have already come forward but I would urge anyone with any information, regardless of how insignificant you think it may be, to contact us. We would specifically like to speak to anyone who was in or around Victory Road between 3am and 4am on Friday morning."
Mr Philpott, said to be the father of 17 children, hit the headlines after demanding a larger house to share with his wife Mairead, girlfriend Lisa, and eight offspring. He was dubbed "Shameless Mick" in 2007 for his benefit claims and refusal to get a job in a TV documentary by former Conservative MP Ann Widdecombe.
Mr Philpott is reported to have demanded the bigger property because his council house was too cramped to accommodate the family. He wanted the city council to rehouse them, but the authority said they already had the biggest available council property in the city.
Ms Widdecombe, who spent a week living with the then 57-year-old Mr Philpott for the programme, Ann Widdecombe Versus The Benefit Culture, said following the tragedy: "Nobody would ever call him a bad father. I'm so sorry to hear the news and my thoughts are with the family."