NSW police have located the young mother of a newborn baby whose body was discovered in the backyard of a Newcastle home four days ago.

On Tuesday, police issued a public appeal for the woman’s whereabouts, concerned for her welfare following the tragic discovery in Stockton.

Newcastle City District Commander Brett Greentree said at the time he was unable to say exactly how recently the baby had been born.

“It’s very difficult to answer that at the moment. This will be a matter for the coroner,” he said.

Commander Greentree said it was “a heartbreaking situation”.

The mother, 18, 
was found in Sydney’s west in Penrith, and has spoken with police about the birth of her child.

“Investigators have ruled out the involvement of any third party,” police said in a statement on Friday.

“Police will await the results of a post-mortem examination and forensic testing to determine the direction of any future inquiries.”

Detectives say their investigation is expected to be prolonged due to the volume of forensic evidence involved.

-with AAP