Police investigating the death of an 11-month-old baby girl last night are treating the incident as a suspected homicide.
A man believed to be the baby's father is being interviewed by police after being released from hospital.
There are reports that the man and the baby were found in a gas-filled house.
An ambulance was called to a carpark on Ranford Road, near the intersection of Nicholson Road, in Canning Vale at 9.40pm.
A caller said a female was with a baby who needed emergency first-aid at the location, police said.
The ambulance performed CPR on the girl, who had suffered gas inhalation and was not breathing.
She was rushed to Armadale Hospital, where she was confirmed as dead.
An ambulance was called to a house on Pricklybark Street in Harrisdale at 10.10pm, a St John spokesman said.
Major Crime Squad detectives are doorknocking the new subdivision today as they try to piece together what happened.
One neighbour told The West Australian she smelled gas last night, but most said they were not aware of the events of last night.
The couple who live at the house at the centre of the investigation moved in about six months ago, neighbours said.
Many of the surrounding homes are still being built.
Major Crime Squad detectives are investigating the incident and anyone with information is asked to call police on 131 444.