A man and a woman arrested after five children were killed in a house fire in Derby have been released without charge.
The man, 38, and woman, 28, from Derby, had been held on suspicion of murder.
The children, four boys and a girl aged between five and 10, died in the fire in Allenton on Friday despite their father's attempts to save them.
Police said they were still treating the fire as suspicious.
The children, who had been sleeping upstairs when the fire began, have been identified as 10-year-old Jade Philpott, John Philpott, nine, Jack Philpott, seven, Jessie Philpott, six, and Jayden Philpott, five.
Their 13-year-old brother, Duwayne Philpott, who was also in the house in Victory Road, remains in a critical condition in a Birmingham hospital.
Assistant Chief Constable Steve Cotterill said: "While I thank those members of the community who have come forward with information I am surprised by how few people have contacted us. Normally in cases of this scale more information is passed to the police.
"I strongly suspect that there is someone out there in the community who knows more than we are being told.
"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."
He said that if anyone had been "confided in" then they should "speak up and do the right thing".
A Derbyshire Police spokeswoman said post-mortem examinations were being carried out to establish the cause of the children's deaths.
Prayers were said for the children at a special service in the town earlier on Saturday and a candlelit vigil is due to be held later.
Locals on the estate where the family lived said they had set up an online charity called Catch Me When I Fall to help the family with funeral costs and anything else they may need.
The children's father, Mick Philpott, is believed to have 17 children.
His family were the subject of media scrutiny in 2006 when he asked the council for a larger house to accommodate his wife, girlfriend and 14 children.
In 2007 former Conservative MP Ann Widdecombe spent a week living with the family as part of an ITV documentary and he also appeared as a guest on the channel's Jeremy Kyle Show.