The mother of a newborn baby boy found abandoned in a drain in western Sydney has been identified.

The 20-year-old from Quakers Hill was tracked down via hospital records and she is now assisting officers at Blacktown Police Station.

Inspector David Lagats said the baby, believed to be about two to three days old, had possibly been taken from a hospital.

The newborn baby was discovered in a stormwater drain in Quakers Hill. (NSW Police)

A cyclist who found the newborn believes the child may not have survived a 2.4m drop into the drain if not for a blanket wrapped around him cushioning the fall.

David Otte, of Rydalmere, and his 18-year-old daughter Hayley were stopped by a group of cyclists, who had gathered around the Quakers Hill storm drain after hearing crying noises around 7.30am.

"I've got two kids of my own so I know what a baby screaming sounds like," Mr Otte told the Sydney Morning Herald .

"It was so intense; you couldn't not tell it was a baby. We couldn't see it but we could hear it. It was distressed."

Six people lifted a concrete slab weighing more than 200kg which covered the drain and discovered the baby boy wrapped in a hospital blanket and covered in dirt with a peg still attached to his umbilical cord.

The drain near the M7 cycle path where a newborn Sydney baby was found dumped. (AAP) (AAP)

Police have indicated that a hole in the slab was just large enough for the baby to fit through and are looking to confirm whether the infant was dropped the 2.4m distance to the bottom of the drain.

Mr Otte said the baby looked "brand new" but its fragile body may have been protected in the fall by its swaddling.

"You go through life seeing things but you never ever imagine you'll see something like this," he said.

"That baby had no chance if we and the other people hadn't of been there. Something made us find that baby today."

Inspector David Lagats, who attended the scene, added: "We all thought the worst but the baby was still alive.

"Once we found out how far the drop was, we were concerned about the baby's welfare but it was wrapped up pretty well"

The baby did not appear to have suffered external injuries but was taken to Westmead Children's Hospital as a precaution.

Police believe the baby was only dropped into the drain this morning, but would have been in grave danger had it not been discovered early, with temperatures in western Sydney set to soar above 40 degrees today.

Officers are following up reports of a man of Indian appearance in an orange shirt seen on the track at about the same time the baby had been discovered.

Family and Community Services western Sydney director Lisa Charet said incidences of babies being abandoned were "rare".

She said the parents, particularly the mother, would need help and support.

"Often, people (who abandon their babies) are in a place of desperation," she said.

She said the mothers often suffered from post natal depression or were young and scared.

Insp Lagats agreed that while it was a "disturbing incident", he could not say for certain that whoever abandoned the baby intended it to come to harm.

"I can't speculate on what the person's intentions were," he said. "They may not have known the drop was so great."

Anybody with information about who the little boy is or how he came to be in the drain, is urged to come forward or contact CrimeStoppers on 1800 333 000.