But just before 12.40pm on Monday, he was found safe and well in the stairwell before being taken to hospital as a precaution.

A medical centre staff member checked the stairwell after police earlier appealed to the public for assistance. 

"He was found in the stairwell, he smiled, he was sitting up," Superintendent Simon Glasser told reporters.

"He has been taken to hospital just for a check up, but on all accounts he's doing well." 

Supt Glasser thanked members of the public for helping police during the search.

"All of our messaging got out to the right people and someone, as a result of hearing that, has gone and searched a stairwell," he said. 

"(The family) rushed to the scene and took him in their arms, they're quite ecstatic." 

More than 200 NSW State Emergency Service volunteers joined a search that also included PolAir and the riot squad. 

Searchers had been experimenting with playing the boy's favourite music in the hope of drawing him out if he was hiding or sheltering due to his fear of strangers.

"The volunteers have given up their weekend (and) a lot of them have given up their day from work today to search for the young fella," SES Auburn unit commander Jamie Newman said. 

"It was a huge weight lifted off our shoulders, knowing that he's been found safe."

Supt Glasser earlier said the boy had previously gone missing but usually for much shorter periods.

"He is 12 years old, he's got special needs and he's been out and about by himself for 48 hours now so it's as high risk as it gets," he said.

"It's already at a critical point so we're throwing everything we have at it and we're going to keep searching."

License this article