Five children died in a house fire today despite "valiant attempts" by their father to rescue them.
Ten-year-old Jade Philpott was asleep upstairs along with John, nine, Jack, seven, Jessie, six, and five-year-old Jayden at their home in Allenton, Derby, when the fire broke out.
Their 13-year-old brother, Duwayne, remains in a critical condition in hospital in Birmingham.
The children's father has been named locally as Mick Philpott, who was dubbed "Shameless Mick" in 2007 for his benefit claims and refusal to get a job in a documentary by former Conservative MP Ann Widdecombe.
Mr Philpott, said to be the father of 17 children, hit the headlines after demanding a larger house to share with his wife, girlfriend and eight offspring.
They are believed to be at Duwayne's bedside in hospital.
A 28-year-old woman arrested on suspicion of murder remains in police custody and will be questioned later, Derbyshire Police said.
Post-mortem examinations will be carried out over the weekend and forensic specialists are examining the house.
Ms Widdecombe, who spent a week living with the then 57-year-old Philpott for the programme Anne 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."
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.
Temporary Assistant Chief Constable Steve Cotterill, from Derbyshire Police, said: "There appears to have been valiant attempts by the father to rescue his children."
He said two adults in the home, whom he did not name, escaped the fire without serious injury after being alerted by a smoke detector.
Mr Cotterill, who said police were keeping an open mind about the cause of the fire, said: "It is a matter of a police inquiry, where we have had to act very quickly to preserve any evidence which may feature later in the inquiry."
It was "potentially" a murder inquiry, he added, and the woman being questioned by police was not arrested at the scene.
The six children were asleep in their beds when the fire broke out, and the two adults, including Mr Philpott, were downstairs.
He said eight people were living in the house on a permanent basis, though there might be other people who stayed there on an ad hoc basis.
Mr Cotterill said: "Our thoughts are with the parents and the family of the children for their tragic loss and for the community of Allenton, who would of course have known the children as they played."
Friends of the family left flowers at the scene.
Daniel Walsh, who said he had been a friend of Mr Philpott for many years, called the fire "shocking", adding: "It's absolutely tragic. Any parent's worst nightmare.
"I didn't know his younger children. He had many children, as everybody knows, and he loved them all the same, no doubt.
"It's just a tragic loss."
Another neighbour, who gave her name only as Kaye, said she saw flames coming out of the house and "loads of ambulances", and described it as a "horrible, horrible" scene.
"I just saw the babies going to the ambulance because it was parked outside our house," she said.
"The children are friends with my kids. They played with my children.
"They were OK, good kids."
Mr Cotterill added: "I am grateful for co-operation from the community in Allenton and their patience during the road closures.
"There will be an increased presence from police and partner agencies in the area during the next few days to offer advice to the community."