Police have been given more time to question a 21-year-old man over the murder and serious sexual assault of a two-year-old girl.
Casey Mullen was found dead in her bedroom at home in Oak Tree Crescent, Gipton, Leeds, on Sunday following a disturbance outside the house.
A post-mortem examination showed she died from "compression to the neck", police revealed on Tuesday.
The arrested man has been named locally as Casey's uncle, Michael Mullen.
Magistrates granted officers an extra 36 hours to question the man on Tuesday afternoon.
Two other men aged 19 and 20 who had been arrested in connection with the inquiry have been released without charge.
A Leeds City Council spokesman said social services had been "briefly" involved with the family in 2005, although no more details were given.
Messages and flowers lined the footpath for a little girl neighbours said was cheerful and known as "Smiley".