Detectives have been given another 24 hours to question a man held in connection with the murder of a mother and her two young children.
Fatimah and Naeemah Drammeh, three and one, died in an arson attack at their flat in Fairisle Close, Clifton, Nottingham, in the early hours of Sunday.
Their mother, Fatoumatta Hydara, 28, was taken to hospital and put on life support but died on Tuesday.
A man from Clifton, 31, arrested on Sunday night, was due to be released on Thursday evening before detectives got an extension to his custody time limit.
It comes as a team of 40 detectives continues to look at CCTV, forensics and other evidence.
Detective Chief Inspector Mark Sinski, who is leading the probe, said: “The investigation is progressing well and we won’t stop until we have got justice for the family.
“Officers have worked tirelessly since the early hours of Sunday morning, building up a picture of what happened on that fateful day.
“This is an horrendous crime that has broken a family and had an immense impact on the Clifton community.”
Paying tribute to his wife and two daughters, Aboubacarr Drammeh, 40, described their deaths as a “cruel crime”.
Nottinghamshire Police said there is nothing to indicate the attack was a “hate crime”.
Mr Drammeh, who flew back from the US after the fire, said: “It is with great sadness that we have lost Fatoumatta and our two daughters in such a tragic way.
“Fatoumatta had lived a short but a very beautiful and fulfilling life. A former voluntary worker, Fatoumatta was a very happy, bubbly woman who wouldn’t have the heart to hurt a fly.
“It is therefore inconceivable to think who might have committed this cruel crime against my family.
“We thank the Ahmadi Muslim community in Nottinghamshire, the Gambian community, the local neighbours and all those well-wishers for their continuous support in this difficult time.
“I and my in-laws are left without any daughters, grandchildren and nieces. I will deeply miss my family.”
Police are appealing for information and are especially keen to speak to anyone on the streets in the area between 12-4.30am on Sunday.