I really do not understand why if LE came to a home, and found a little girl almost dead, that the people in the house would not be arrested on the spot. Maybe it wasn't obvious that it was murder at first, but they have ruled it a homicide.
There's a reason why parents who kill their kids dump the bodies. The ones who don't....get arrested! Look at the "Crimes Against Children" forum---case after case of parents or their significant other killing the kid, calling 911, saying it was an accident, and being arrested on the spot.
This makes me think that the case is more complicated than that. Perhaps LE has a suspect, a family member, but they need to prove they were there; like maybe this family member left before LE got there? IDK.