A member of the public reported locating the baby in the yard of their Copernicus Way home in Keilor Downs shortly before 8am, according to authorities responding to the scene in Melbourne's north-west.
The baby and a woman from a nearby address were taken to hospital for treatment. Both remain in a stable condition, with paramedics arriving at the scene to provide immediate care following the discovery.
Brimbank Sexual Offences and Child Abuse Investigation Team detectives are investigating the circumstances surrounding how the infant came to be abandoned. Investigations into the circumstances surrounding the incident remain ongoing.
The discovery raises urgent questions about the welfare of the mother and the circumstances that led to the infant being left in the yard. Police have not yet provided details about the condition of the newborn or the identity of the woman who was also taken to hospital.
Members of the public who have information about the incident are being urged to contact Crime Stoppers Victoria on 1800 333 000 or visit www.crimestoppersvic.com.au to submit an anonymous report.
If anyone is aware of a woman who may need support or medical care following childbirth, Lifeline can be contacted on 13 11 14 or Beyond Blue for mental health support. In the event of an emergency, Triple Zero (000) should be called immediately.