Police confirmed late on Monday that bones found in the bushland belonged to a small animal

The search is expected to last several days while up to 30 officers comb through thick overgrowth and muddy tracks between Bonny Hills and Lake Cathie on the state's mid north coast.

William was wearing a Spider-Man suit and playing with his sister in the garden of his grandmother's Kendall home almost six months ago.

Homicide commander, Superintendent Michael Willing, said police were searching for evidence in relation to William's suspected abduction but were not digging for a body.

"This will not be the last search in regards to this investigation," Superintendent Willing said. "There is always that possibility [of finding a body] but we are searching for evidence at this point."

The head of the investigation, Detective Inspector Gary Jubelin said the fresh information was received well after police searched the Bonny Hills home and Laurieton office of washing-machine repairman Bill Spedding.

"The search is based on recent information we have received and where a few lines of inquiry has taken us. This is fresh information," Inspector Jubelin said.

"What that evidence is, and whether it goes as far as a body, we simply don't know. But it is not a search specifically for a grave site."

In January, police used an excavator and drained a septic tank at Mr Spedding's semi-rural property in Wandoo Place.

They also searched Mr Spedding's pawnbroker business in the nearby town of Laurieton.

Mr Spedding has denied an involvement in William's disappearance and is backed by two of his children.

"We fully support him. We know that he has had nothing to do with this," his daughter-in-law told Fairfax Media.

Police have said Mr Spedding is not a suspect.

"At the very highest, he is a person of interest but he is not the only person of interest," Superintendent Willing said.

At the time his home was searched, Mr Spedding said the police search had been difficult for him and his family, and that he and his wife were on the verge of having nervous breakdowns.

Mr Spedding had visited the home of William's grandmother four days before the boy's disappearance after a request to repair a washing machine.

A close friend, Colin, said Mr Spedding did not return to the grandmother's house with a spare part for the washing machine on the day William went missing because he could not get in contact with her.

Strike Force Rosann had been established to investigate William's disappearance.

Anyone with information has been urged to contact Crime Stoppers on 1800 333 000.