A three-year-old boy who went missing from his family's NSW Hunter Valley property on Friday has been found alive after four days of intensive searching in rugged bushland.

Police tweeted on Monday afternoon the boy had been found but was yet to be assessed by NSW Ambulance paramedics.

Anthony "AJ" Elfalak, who has autism and is non-verbal, went missing from his family's remote rural property at Putty about 11.45am on Friday.

He was reportedly found by a rescue helicopter in nearby bushland.

Premier Gladys Berejiklian said she would be "absolutely delighted" if the then unconfirmed reports the boy had been found were true.

"I think all of us have been crossing everything to make sure AJ is brought back safely," she told reporters.

"And if that's the case, it's much-needed good news in otherwise difficult circumstances."

Anthony and Kelly Elfalak and their four sons moved to the property just months ago as Mr Elfalak's work as a plumber had dried up amid the COVID-19 lockdown.

Family friend Alan Hashem was at the property when the boy went missing and says he saw an old white van driving away from the location.

He said the family believed the boy has been abducted.

"Without a doubt. Without a doubt," he told the Nine Network on Monday.

"For the simple reason he is on the spectrum of autism but he is always quite afraid and attached to his mum hence why his mum couldn't have him by her side when she's cooking, he is with his brothers.

"He's never wandered," he said.

NSW Police Superintendent Tracy Chapman said over the weekend more than 130 people were involved in the search of the property and volunteers helped police on foot and on dirt bikes.

Divers also searched and drained a large dam on the property.

© AAP 2021