Police investigating after newborn baby found in Melbourne backyard

An investigation is underway after a newborn baby was found in a backyard in Melbourne's north-west.

A member of the public reported finding the baby in the yard of their home in Keilor Downs shortly before 8am today, police said.

Paramedics arrived at the scene, before the baby and a woman in her 20s were taken to hospital for treatment.

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The woman was found at a home that backs onto the property where the baby was located.

The SES has set up a tent in that backyard and blocked off the street as they turn their focus to the woman's movements.

Witnesses say there were items of bloodied clothing or towels left on the front nature strip near where the child was discovered.

"We heard inside here, a noise about 7:45-8am. Just sort of a noise, a bang," neighbour Michael Tait said.

"Didn't sound like a gunshot or anything, just some sort of strange noise and then the next noise that happened was an emergency vehicle coming up our street."

It's unclear at this stage exactly when the baby was born and the circumstances surrounding the birth.

The baby and the woman are both in a stable condition at Sunshine Hospital.

Anyone with information is urged to contact Crime Stoppers.

If you or someone you know is in need of support contact Lifeline on 13 11 14 or Beyond Blue. In the event of an emergency dial Triple Zero (000).