A search for a missing autistic boy remains focused on a part of the Mille Iles River, near a waterfront property where three-year-old Adam Benhamama was last seen alive.

Police increasingly suspect that the young boy, who is also unable to speak or hear, fell into the river after he went missing on the weekend.

Benhamama was playing outside with his sister at a home of a family friend in Laval, Que., whom the two siblings were visiting with their father.

The boy slipped out of sight during a game of hide-and-seek while his father was momentarily inside the house.

The boy's absence was quickly reported to police, who brought in dogs, ATVs, extra officers and eventually divers to try to find him.

CTV Montreal's Cindy Sherwin said police have put "all their resources" into the desperate search for Benhamama, including flying a helicopter over the property.

But after two nights of cold and wet weather, Laval police spokesperson Nathalie Lorrain said it seems unlikely that the young boy could have survived on his own, without food or shelter.

"Definitely the hope that he would still be alive if he was outside is very slim," Lorrain told CTV Montreal on Tuesday.

Sherwin said police divers are now trying to remove ice from the surface of the river, in anticipation of the tragic possibility that they will find Benhamama's body in the water.

Earlier Tuesday, CTV's Genevieve Beauchemin reported that police intended to speak to Benhamama's seven-year-old sister on Tuesday, with hopes of obtaining more clues as to where her brother may have went when he disappeared.

Benhamama's parents have been keeping a low profile since their son went missing and they have not spoken to the press about their ordeal.

The boy's mother was not at the property when Benhamama went missing. Police say she went into shock when she heard what happened to her son.

Carol Namur, the founding president of the volunteer group Sauvetage Canada Rescue, said it is well possible that Benhamama stayed relatively close to the area where he was last seen.

Namur said autistic children "are more likely to just stop, and rock back and forth, and save energy" when they end up separated from loved ones. The fact that Benhamama is only three years old may also have limited how far he wandered.

"When you combine those two elements, it means that there's a very good chance also that he has found a hiding place," Namur told CTV's Canada AM during an interview from Montreal on Tuesday morning.

Benhamama has dark hair and was wearing a black jacket, blue jeans and a striped toque when he went missing. He is two feet tall and weighs 25 pounds.

Police are asking members of the public to approach the missing boy gently if they see him and to contact authorities as quickly as possible.

With files from The Canadian Press