NSW Police Commissioner Mick Fuller said in a national radio with 2GB that he believes the investigation 'will be solved' and confirmed there is 'one person in particular (they) are looking at'.

"The team is working diligently ... we are hopeful we will find some forensic evidence that will help us solve this case," Commissioner Fuller said.

Hundreds of police have descended once again on Kendall on the Mid North Coast for a series of "high intensity" searches following the revelation there is new evidence in the investigation.

William Tyrrell was just three-years-old when he went missing from his foster grandmother's yard in Benaroon Drive, Kendall on September 12, 2014.

The little boy wearing a Spiderman suit was playing with his sister, growling like a tiger when in an instant, he was gone. He has not been seen since, nor has there been any definitive evidence of what might have happened.

In that time investigators working in Strike Force Rosann have looked at thousands of pieces of evidence and conducted interviews with hundreds of person of interest.

They have been working under the premise that William's disappearance was as a result of human intervention. A $1 million reward was offered for information that lead to William being found.

That narrative changed this week when Detective Chief Superintendent Darren Bennett said in a media conference on November 15 that Strike Force Rosann were "looking for the remains of William Tyrrell".

It has been the first time it has been assumed by police investigators that the child is dead.

"It's highly likely that if we found something it would be a body," Det Ch Supt Bennett said. "We are looking for the remains of William Tyrrell, there's no doubt about that."

Commissioner Fuller reaffirmed the purpose of the current sweep of three locations off Batar Creek Road, not far from where William disappeared, is to bring the investigation to a close.

He said the current team, headed by Chief Inspector David Laidlaw, was one of the "best teams we've seen".

"We've never given up on finding what happened to William Tyrrell and we've said that from day one," Commissioner Fuller said.

"It is not a cold case, it's an active investigation."

Commissioner Fuller said the Strike Force's strategy is to conduct searches using some of the state's best forensic teams and equipment.

This week's search will involve the clearing of trees and digging at key sites. Specialist cadaver dogs have scoured the areas in question.

One of the locations is off Cobb and Co Road, while the other includes a return to the grounds of the home on Benaroon Drive where gardens underneath the balcony are being turned over.

Commissioner Fuller was critical of earlier investigative work where he believes time was wasted.

"These areas have been searched but initially we were searching for a missing boy," he said.

"The transition of the investigation was looking at some persons of interest that were clearly not, and I think some time was wasted on that. A fresh set of eyes, under Chief Inspector Laidlaw, have been meticulously pulling apart this matter.

"It is my understanding from the investigators there is certainly one person in particular we are looking at.

"I'm confident the team who has the investigation at the moment can solve it."

Commissioner Fuller also confirmed that NSW Police have sought an apprehended violence order (AVO) against William Tyrrell's foster parents, allegedly in relation to a child linked to William.

Commissioner Fuller would not comment any further on that aspect of the investigation.

William's foster parents issued a statement on September 7 critical of news reports that claimed NSW Police had a new person of interest in the case.

"Imagine waking up to an unsubstantiated article published by a large NSW media outlet claiming that a senior officer within NSW Police has shared that they have a new person of interest, whilst inferring that this heinous crime is on the brink of being solved. Once again we are forced to watch others objectify William for personal gain," the statement said.

"Time and time again weve watched people lose sight of the tragic reality that William was a precious, innocent little boy who was taken from those he loved and who love him deeply, forgetting that there is a heartbroken family waiting in hope that William will be found.

"To publish unverified claims, without consideration to the hurt that articles of this nature cause is disrespectful and devastating to everyone who knows and loves William."

Homicide detectives returned to Kendall on the seventh anniversary of William's disappearance on September 12.

The team, originally led by Gary Jubelin who resigned after allegations were proven he had made illegal recordings during the investigation, have conducted numerous searches over the years between Kendall and Herons Creek.

A coronial inquest commenced into William's disappearance in March 2019 and remains ongoing. It is being overseen by Deputy State Coroner Harriet Grahame.

The inquest has considered thousands of pieces of evidence collected by Strike Force Rosann, statements by persons of interest and recollections by family and neighbours of the morning William vanished.

The inquest concluded in Lidcombe Coroner's Court in Sydney on October 8, 2020. with an emotional plea by his 10-year-old sister - "I will find my brother and not give up until he is found".

The coronial inquest findings were to be handed down by Deputy State Coroner Grahame in June 2021. A new date has not been determined.

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