The much-awaited autopsy has failed to determine the cause of death of three-year-old Indian boy Gurshan Singh, whose body was found near here after he went missing from his house, Australian police said on Friday.
Victoria Deputy Police Commissioner Sir Ken Jones said: "There is no visible signs of the cause of death."
Jones said the boy's parents were being interrogated.
"At the moment we're desperate for witnesses to come forward. We're pretty convinced there's people out there that may have seen something," he said.
He said police have not yet determined if the boy's death was an opportunistic crime or something else.
"We just don't know at this time and I don't want to speculate and try to keep people focused on the facts as we know them," he said.
"It's clear that this wasn't death from natural causes, but we don't yet have a 100 per cent conclusion on what the actual cause of death was."
Gurshan was in Australia on holiday with his family and was due to return to India later this week. His body was found around 30 kms away from his residence yesterday.
Victorian state police said a council worker found the toddler's body in long grass.
Australian Prime Minister Kevin Rudd has condemned the toddler's death, calling it a "brutal thing to happen". Police were treating the incident as a "worst case" and have deployed all available resources to investigate the suspected homicide.