Three men have been arrested on suspicion of murder after three people, including a young mother and her baby daughter, were killed in a house fire.
Amy Smith, 17, her six-month-old daughter Ruby-Grace Gaunt and friend Edward Green, also 17, died in Langley Mill, Derbyshire, early on Sunday.
The baby's father, Shaun Gaunt, and two other people are believed to have also been caught up in the blaze.
Derbyshire Police said: "A 17-year-old from Long Eaton, and a 21-year-old and a 43-year-old from Sandiacre, were all arrested late last night on suspicion of murder.
"The three men remain in custody this morning and are being questioned.
"Officers are still working closely with Derbyshire Fire and Rescue Service to ascertain the cause of the fire, which is still unknown at this stage."
Assistant Chief Constable Martyn Bates said: "The cause of the fire is still unknown and the possibility that it was started deliberately is just one of many lines of inquiry we are pursuing at this time.
"These arrests do not mark the end of the investigation, far from it. I would still urge anyone with information to come forward and speak to us."
One fire appliance was sent to the scene after Derbyshire Fire and Rescue Service (DFRS) was initially called to a car fire in North Street at 3.59am on Sunday.
A further three crews were dispatched following a call two minutes later reporting the house fire. Emergency services received more than 20 calls about the blaze.
Speaking at the scene yesterday afternoon, Derbyshire Assistant Chief Fire Officer Gavin Tomlinson said the fire started in the ground floor area.
He said: "We'll go through and try and rule everything out we possibly can until we come to a conclusion. It will take as long as it takes to make sure no stone is left unturned."
Neighbour Paul Barber, 33, who lives in the flat next door to the one affected, said he and his wife were woken at 4am by banging on their door alerting them to the blaze.
Mr Barber said they ran outside and could see a "big glow" and high flames.
He said: "People were screaming for help, it was very chaotic. I saw one person throwing their child out of the window on to a mattress to get him safe.
"It's a big shame, they were a very cute family."
A tribute site has been set up in memory of those who died.
Jodie Mee wrote: "Rest in peace girls and Ed, heaven has gained two beautiful girls and a strong boy. Thoughts go out to their family and all the people who knew them.
"(They're) in a safe place now, Ruby will be in mummy's arms and Ed will be standing by them both. Fly high beautifuls, sleep tight."
Another, writing as Lewis Ph, added: "Love you bro, I'll never forget the times we had together. We were close mates for a long time, best mates. You were like a brother to me and nothing will ever change that. RIP brother."
Leanne Marie said: "Three young people taken too young. Such an awful thing to happen. My thoughts are with the families at this awful time."