The parents of a seven-week-old baby were last night being questioned on suspicion of her murder.
A 28-year-old man and a woman aged 18 were originally arrested on suspicion of assault after police were called to the hospital where the baby was admitted.
But the investigation was changed to a murder probe after the infant died at around 3am today.
A neighbour said the family had been rushed in to hospital on Thursday morning and police had been stood outside their rented semi-detached home ever since.
Neighbour Keith Coverdale said he had seen little of the couple since they arrived in the street - and even less of their child.
Mr Coverdale, 28, said: ‘The only clue I had that there was a young child in the house was the babygrows I would see hanging on their washing line.
The only conversation I have had with them was on Tuesday night, when I took my dogs out for a walk.
'They were returning home with a baby in a pushchair and warned me to keep the dogs away from their gate.’
Mr Coverdale, a full-time carer for his partner, added: ‘That is the only time I have seen either with a child, but the infant I saw looked a lot older than seven weeks. I thought that baby was around a year old.’
The couple moved to the rented property three-bedroom home in Pontefract, West Yorkshire, in February.
Paul Rothwell, 67, the owner of the property, said he understood the couple moved in before they had the baby.
He said the house is managed by a letting agency, who in turn sub-let the property to a social housing company which specialises in accommodating ‘vulnerable people’.
It is understood either one or both parents was already receiving some sort of support from social services prior to the child’s birth.
Local labour ward councillor Tony Dean said he had been electioneering in the street yesterday.
‘There were a couple of PCSOs and a constable in the road but they didn’t say what they were doing’, he said.
‘It’s a reasonably prosperous area not known for anything as tragic as this’, he said.
West Yorkshire Police said a murder investigation had been launched after the baby girl died from her injuries in Pinderfields Hospital, Wakefield.
Officers were called to the hospital on Thursday night following the child’s admission by ambulance with ‘serious injuries’.
A police spokesman could not elaborate on the nature of the injuries ahead of a post mortem examination which was taking place last night. .
The couple remained in custody last night.
A spokesman for Wakefield Council confirmed the family was known to social services.
He added: ‘It’s obviously a really sad event but I cannot comment further in view of the police investigation.’