An eight-year-old girl attacked at a house near Walsall died from a single stab wound to the chest, a post-mortem examination has found.
Mylee Billingham died in hospital after police were called to a house in Brownhills at 9.15pm on Saturday.
West Midlands Police said at the time that she had suffered serious stab injuries, with father Bill Billingham also found with a stab wound to the stomach.
He was arrested on suspicion of attempted murder, but on Tuesday that was changed to murder.
The 54-year-old will be interviewed by officers “when deemed medically fit”, as he is expected to require surgery after being taken to hospital in a critical condition.
In a short statement issued on Wednesday, West Midlands Police said: “A post-mortem examination took place on Monday and the results confirm that Mylee died of a single stab wound to the chest.
“The 54-year-old man remains in a serious but stable condition in hospital. Police continue to support Mylee’s family at this tragic time.”