A man and a woman who were arrested on suspicion of murder in connection with the deaths of five children in a house fire have been released without charge, police said.
The 28-year-old woman and 38-year-old man, both from Derby, were arrested on Friday by officers investigating the deaths of 10-year-old Jade Philpott and her siblings John, nine, Jack, seven, Jessie, six, and five-year-old Jayden.
The children died after a fire ripped through their home in Victory Road, Allenton, Derby, in the early hours of Friday.
Their 13-year-old brother Duwayne, who was also in house at the time of the blaze, remains in a critical condition in hospital in Birmingham.
Assistant Chief Constable Steve Cotterill said: "This is a complex inquiry which requires careful and methodical investigation. We are still treating the fire as suspicious and are pursuing a number of lines of inquiry."
The children's father, Mick Philpott, who 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, made a "valiant" attempt to save them, police said.
Said to be the father of 17 children, Mr Philpott hit the headlines after demanding a larger house to share with his wife, Mairead, girlfriend, Lisa, and eight offspring.
The children were asleep in their beds upstairs in the house when the fire broke out at the pebble-dashed semi-detached home in the early hours of Friday morning.
Mr Cotterill offered his thanks to members of the community who had approached police with information but said he was "surprised" by how few had contacted police.
"I strongly suspect that there is someone out there in the community who knows more than we are being told," he said. "I fully understand that people may be reluctant to talk to us. My plea in this case is to remember that we are trying to find out exactly what caused the death of these five young children, who had everything to look forward to in life. If someone has confided in you, now is the time to speak up and do the right thing."