The much-awaited autopsy has failed to determine the cause of death of three-year-old Indian boy Gurshan Singh, whose body was found in Melbourne after he went missing from his house, the Australian police said.
The Victoria Deputy Police Commissioner Sir Ken Jones said: "There are 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."
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.
