The search for a missing 12-year-old non-verbal Sydney boy with autism and Down Syndrome is at a “critical stage” on day three, as police frantically chase potential sightings over the last 24 hours.

Superintendent Simon Glasser said Hussein Al Mansoory’s multiple conditions leave him “very vulnerable”, particularly given soaring temperatures over the weekend, and make the task of finding him extremely challenging.

A huge team of police and over 100 SES specialist staff are searching the Auburn council area in Sydney’s south-west, as it was revealed Hussein is wearing a white t-shirt, a nappy and no shoes, “which highlights his vulnerability”.

Hussein Al Mansoory, 12, has been missing from Auburn since yesterday morning. (NSW Police)

“We’re were highly concerned, this is as high risk as it gets for us with a missing person,” Glasser said.

Police have deployed choppers which are broadcasting messages from loud speakers above, hoping to reach Hussein who could be hiding out in the suburbs many commercial and warehouse environments or on private land.

Glasser said there appeared no “sinister” signs behind Hussein’s disappearance but that police were ready to switch modes if alternate information came to light.

“At this point where we’re dealing with it as a boy who’s wandered off,” he said.

“We’ve always got (different scenarios) in the back of our mind. We’re not going to lose time in case it does go that way.

“However at this point we’ve got nothing to suggest it’s anything sinister.”

Hussein has been missing since Saturday morning when he was spotted running from Auburn Memorial Park towards the intersection of Station Road and Rawson Street.

He was later seen about 9pm that night near Norval Street.

Glasser said there had been two confirmed sightings of Hussein on Saturday and a number of possible sightings on Sunday.

“We’re throwing everything we’ve got at it,” Glasser said.

Hussein Al Mansoory
Police have reviewed CCTV from the area, looking for Hussein Al Mansoory. (Supplied)
Superintendent Simon Glasser said the search for Hussein Al Mansoory is now 'critical'.
Superintendent Simon Glasser said the search for Hussein Al Mansoory is now ‘critical’. (9News)

Hussein could “certainly be further afield” than somewhere in Auburn, Glasser said, but he indicated the boy was more likely be wandering or hiding out locally.

Glasser said anyone who spots Hussein should call triple zero and stay on the phone and not approach him, “because that could cause him to run off”.

Police had their fingers crossed Hussein had found some food, as “that would be a struggle for anyone, even without special needs,” Glasser said.

Police have reviewed CCTV footage and confirmed Hussein did not catch a train from Auburn Station. A police air and land search has so far come up empty.

Police and SES began their search again today in and around Auburn but will expand the radius as the day progresses. (Nine)

“Past history suggests he usually stays local,” Glasser said, describing other times Hussein has temporarily vanished. There are no plans at the moment to search outside the Auburn LGA.

Glasser said Hussein’s parents were distraught.

SES Commander Jamie Newman said his teams had searched “a lot of the LGA in different with different search techniques” and would widen the area if police requested.

SES Commander Jamie Newman said a team of more than 100 had scoured the Auburn LGA
SES Commander Jamie Newman said a team of more than 100 had scoured the Auburn LGA (9News)
Locals are joining in the search efforts, hoping Hussein is reunited with his family. (Nine)

Locals have joined the search, hoping to reunite Hussein with his family.

“I got the text message on it. I was driving around but didn’t see anything,” one resident told 9News.

Police and SES are searching the area again today.

A hot weekend in Sydney with temperatures running around 30 Celsius has heightened concerns for Hussein’s welfare and amplified the urgency to find him.

Temperatures are expected to hit similar highs today.

Hussein is described as being of Middle Eastern appearance, of slim build, about 140 centimetres tall, with short black hair, and last seen wearing a white T-shirt.

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