In addition to the massive search operation, forensics detectives spent the night collecting evidence from around the property.

AJ, who has non-verbal autism, was playing with his brother at the family's 650 acre property off Yengo Drive in Putty when he disappeared just before midday on Friday.

Police are continuing to investigate the possibility that AJ may have been kidnapped.

A suspicious older model Toyota Hilux was seen on the private road surrounding the property about the same time AJ went missing.

More than 130 emergency service resources spent Saturday searching for the boy.

An emergency text message was also circulated across the region appealing for information.

Hunter Valley Police District commander Superintendent Tracy Chapman said the terrain was "difficult" with various levels of elevation.

"We have been searching the dams and waterways," she said. "Every minute is important."

Anyone with information about this incident is urged to contact Crime Stoppers: 1800 333 000 or https://nsw.crimestoppers.com.au.

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