The focus of the investigation had remained on what happened to Atreyu, Mr Bourke said.
A post mortem was completed yesterday, but police said they would not release the results.
Twenty-five staff are working on the homicide inquiry.
None of the neighbours said they heard noise from the Carlton Cres house that might have indicated a baby's life was endangered.
In a macabre coincidence, the scene is less than 100 metres from where toddler Tinishar Walker received debilitating head injuries at the hands of her mother's boyfriend three years ago.
Tinishar, 17 months old when she was injured, is permanently disabled after Lance Corkery shook and then twice dropped her on her head in a violent reaction to her crying.
Corkery was given a prison sentence of less than five years.