New evidence could determine exactly what happened to missing boy William Tyrrell with police conducting a fresh search for his body.
Detective Chief Superintendent Darren Bennett said the searches will last two to three weeks and some would be "subterranean" involving hundreds of police officers.
"It's highly likely that if we found something it would be a body," Mr Bennett told reporters on Monday.
"We are looking for the remains of William Tyrrell, there's no doubt about that."
Det Chief Supt Bennett said the search is in response to evidence obtained in the investigation with the focus on three locations in the Kendall area on the NSW Mid North Coast.
He was asked if the evidence was new or old information which was being looked at again.
“This is in relation to information we have received, no doubt about that,” he said.
“There is an investigative review that has been undertaken as an ongoing process but there is also new evidence.”
He also reminded people a $1 million reward remains for anyone with information leading to a conviction.
“I believe it will take us a degree towards proving an offence of finding out what happened to William Tyrrell. I'm not anticipating a swift end to the investigation by any means,” he said.
The three-year-old was last seen wearing a Spider-Man suit in the garden of his foster grandmother's home in Kendall in 2014.
Within hours residents and emergency service workers combed the scrub, creeks and paddocks for him.
Police formed the view the disappearance stemmed from human intervention, and in March 2019 a coronial inquest was held into William's disappearance.
Homicide detectives in September returned to Kendall on the seventh anniversary of William's disappearance.
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