The newborn was found in a piece of clothing on Australia Day on top of a top-loading machine, but died before paramedics arrive.
Police said that a woman living at the home ins the Bald Hills suburb was the mother of the child.
A police spokesman Mark Ainsworth told reporters the woman in her 30s had denied she was the infant’s mother.
“She is saying she didn’t know she was pregnant,” said Ainsworth.
“There was a whole family living in the residence,
“The couple and their children,” he said.
Family and friends are being interviewed as part of the investigation with which the mother is said to be partly co-operating.
Ainsworth appealed to anyone with information to come forward.