Emergency services responded to reports a child had been discovered inside the drain in Alexander Heights about 1pm (3pm AEDT) today.
Multiple resources attended the scene on La Salle Road, which was closed to the public.
Tradespeople working on the storm drain sounded the alarm after making the shocking discovery.
A number of ambulance crews were called but stood down soon after when they realised there was nothing they could do to save the infant.
This evening, police issued an emergency alert to all Perth maternity hospitals with concerns for the welfare of the mother.
This afternoon, detectives dedicated significant time to speaking with every neighbor on the street, seeking CCTV footage, and inquiring if they had observed any suspicious activity over the last 48 hours.
They were expected to remain on the scene for some time.
The age and gender of the child have not been confirmed.
An investigation into the discovery of the child’s body is ongoing.
Anyone with information is urged to contact police immediately on 131 444.
