A 21-year-old man has been arrested over the murder and serious sexual assault of a two-year-old girl found dead in a pool of her own blood.
Casey Mullen was found dead in her bedroom at home in Oak Tree Crescent, Gipton, Leeds, on Sunday following a disturbance outside the house.
The arrested man has been named locally as Casey's uncle, Michael Mullen.
A post-mortem examination showed the child died from "compression to the neck", police said.
Two other men aged 19 and 20 who had been arrested in connection with the inquiry were released without charge on Tuesday morning.
Messages and flowers lined the footpath for a little girl the neighbours said was cheerful and known as "Smiley".
Residents spoke of hearing a disturbance outside the house on Sunday.
Keith Beaumont, 58, who lives close to the house, said: "There was a lot of commotion going on, and a lot of shouting. There were lads banging at the window, shouting and carrying on.
"The police and paramedics came and there was an ambulance.
"They brought the baby out and she was looking very ill."
The scene was cordoned off as tests were carried out
Mr Beaumont said he had spoken to Sarah Pringle, who lives next door to the murdered girl. Ms Pringle had tried to resuscitate the child.
"She did her very best. She tried to revive the little girl.
"She ran upstairs, found the baby, and tried to give her mouth-to-mouth resuscitation."
He said Ms Pringle was "absolutely distraught".
Speaking of Casey he added: "It's absolutely horrendous. We've never seen anything like this in the area."
Local councillor Rev Alan Taylor, who is the vicar of St Aidan's, a parish close to the estate, said: "Whenever a young life is lost under such tragic circumstances it's very sad indeed.
"My thoughts are with the immediate family, I'm very concerned for them at this time."
The West Yorkshire Police force's Homicide and Major Inquiry Team is investigating the death.
A Leeds City Council spokesman said social services had been "briefly" involved with the family in 2005, although no more details were given.