Tradesmen discovered the infant inside a drain on La Salle Road in Alexander Heights about 1pm (3pm AEDT) on Monday.

Growing tributes of flowers and toys have been left at the scene since the discovery.

Detective Senior Sergeant Stephen Cleal yesterday said the baby appeared to have been deliberately placed in the drain “in recent days”.

He said the discovery was “very distressing” for the tradespeople and called on the mother to come forward.

”We want to help that mother,” Cleal said.

“We have serious health concerns for that mother.

“Our priority is to get her the medical help that she needs.

“If you are watching, if you are listening, if you are that mother, please come forward and make yourself known to police, we would love to help you.”

Detectives were canvassing medical centres and hospitals – which were asked to be on alert – and examining CCTV footage of the area but were unsure of the child’s nationality or other identifying details.

Premier Roger Cook described the incident as a “horrifying scenario”.

“The mother of that child must be incredibly distressed,” Cook said.

“Those workers that discovered the child’s body were confronted with the most distressing of circumstances.

“My heart goes out to everyone involved in this horrible, horrible series of events.

“This goes to the heart of everyone’s sense of humanity, a small child whose life has passed under tragic circumstances.”

Anyone with information is urged to contact police immediately on 131 444.