Superintendent Steve Nibloe said: "This is clearly a very upsetting incident and we already have a number of officers dealing with this at the scene and making other enquiries.
"We do not know with any certainty how long the baby has been there or how it has died and while I understand there will be concern in the community I want to reassure residents that we will be working hard to answer these questions.
"If anyone has any information whatsoever, regardless of how insignificant you think it might be, please get in touch.
"We are obviously deeply concerned for the welfare of the mother and if anyone has seen someone in the area or has any information about who you think the mother might be please call us."
Anyone with any information is asked to call police on 101.
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Police said the child, who was without a driving licence, was trying to make his way 2,500 miles from the east coast to Perth.
The 24-year-old was charged with 14 counts of wounding with intent to do grievous bodily harm and one count of throwing a corrosive fluid.