NSW Police Minister David Elliott says all potential and past scenarios are being looked at again.
"An appropriate investigation would review all scenarios whether they've been looked at or not. I'm not going to pride a running commentary on what Mr Jubelin's opinions are."
On Thursday, Federal Police began using specialist equipment on the concrete inside a garage where the boy was last seen.
The ground-penetrating tool will search the foster grandmother's home in the search for the missing boy's remains.
Two sites are of focus in the latest search, the property and a surrounding bushland a kilometre from the home.
Police confirmed on Wednesday they had seized a car in Sydney relating to the investigation, the car had belonged to William's foster grandmother, who passed away in March this year.
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