A baby boy whose body was dumped in a shopping bag at a country bus stop was as young as 24 hours old and still had his torn umbilical cord attached.
A lone woman carrying a similar bag, spotted at the scene in northern Victoria the day before, may be the baby's mother, police believe.
Detectives have appealed to the woman to come forward, and say the mother will need medical treatment.
Because the boy's umbilical cord was not surgically cut, police believe the baby was born outside a hospital and may have been stillborn.
Farmer Paul Hughan found the body in Ford Street at Grahamvale at 5.30pm on Wednesday night when he put his garbage bins out. At first he thought it was rubbish.
"He noticed the shape of a baby and froze in shock, he thought `surely not'," Mr Hughan's son Shane said on Thursday.
The baby was dressed in a blue jumpsuit and yellow singlet and wrapped in a blanket.
After hearing of the discovery, a man contacted police to say he saw a woman by herself at the scene on Tuesday night, said Detective Sergeant Graham Guy, of the homicide squad.
"We have a witness that drove past the bus stop between 5pm and 6.45pm on Tuesday night and told us that he saw a white or silver coloured sedan parked in front of that bus stop," Det Sgt Guy said.
"One female was near the rear of the car and was seen to be holding a green environment bag similar to the bag the child was found in.
"She is described as in her 20s to 30s with fair hair."
Det Sgt Guy said the boy's mother would need urgent medical care.
"She's got nothing to fear from us, we just want her to come forward ... we can discuss the issues that went on later," he said.
"It's hard for me to comment about what's going through her mind, quite obviously she was in a pretty stressful situation to do what she's done and these are the issues we would like to get some help for her with."
The case is not being treated as murder, with an autopsy conducted on Thursday proving inconclusive. More tests will be conducted on Friday.
Mr Hughan was too upset to talk about the discovery but his son Shane said his father noticed the bag, thought it was rubbish and planned to put it in his bin."
He was shocked to discover its contents.
"The first thing he noticed was how lifeless and ridiculously cold it was," said Shane Hughan, 27.
"He put the parcel in the car and told his wife: `I need you to come out and see something, tell me what I am seeing is what I am seeing'.
"They spoke to the next-door neighbour to confirm it too."
Another Ford St resident, Liana Trimboli, 19, said her school-age brother and sister did not want to get back on the school bus.
Ms Trimboli's neighbour Darren Jones, 25, said the incident followed a murder in the same street several months ago, in which a man's body was hacked to pieces.
Police want to hear from family members or friends of a pregnant woman with whom they had lost contact, or from hospital or medical staff with any information about the woman's identity.