Newborn found dead under Melbourne tree

A newborn baby found dead in Melbourne had been hidden under a tree.

The baby was discovered near a footpath in St Albans, in the city's west, after police were called.

An 18-year-old woman who lives near the area was then questioned and released.

"Inquiries are continuing into how long the deceased child may have been there and the circumstances under which it was placed there," a police spokeswoman said on Friday.

She said the newborn had been "concealed" under a tree, near the footpath along Ruth Street.

The death was first reported to police at 3pm (AEDT) on Thursday.

Police Chief Commissioner Ken Lay said the investigation is still in its very early stages.

"We do have some positive leads that we are pursuing," he told reporters.

The homicide squad is still waiting on results from a post-mortem examination to determine a cause of death.

It is not known if the baby is a boy or girl or what relationship, if any, the questioned teenager had with the child.

Investigators want to hear from anyone who saw unusual activity in the Ruth Street area during the past week to contact Crime Stoppers on 1800 333 000.