An intense ground search operation for Adam Benhamama was called off late Monday as authorities failed to turn up any sign of the missing boy, who can't hear or speak.
Police dogs, helicopters and foot patrollers combed the woods all day but failed to find any evidence that the boy might have wandered into the forested area bordering Laval's Auteuil neighbourhood.
"There is no sign at all in the woods that he may have gone in there," Laval Const. Nathalie Lorrain said.
Quebec police divers also scoured the icy Mille-Îlles River, where they plan to resume search efforts Tuesday.
"As time goes by, we're not losing hope, but we think, more and more, that something bad has happened, and he fell into the river," Lorrain said.
Benhamama was last seen Sunday afternoon on Pointe-aux-Ormes Street, where he was visiting friends with his family. He was playing outside with other children when he disappeared.
Polic said he has autism, is deaf, and can't speak, which complicated search efforts.
"It's almost impossible to communicate with him, and also if something happened he couldn't scream or anything like that," said Lorrain.
A search was organized Sunday afternoon after Benhamama was reported missing.
Four police officers continued looking overnight for any sign of the boy along Laval's residential streets.
Family friend Fouad Zhim, who owns the home the Benhamamas were visiting, told CBC that Adam's mother was taken to hospital Sunday, suffering from shock.
The boy's father was at the home Monday, waiting for news.
Adam is two feet tall and weighs 25 pounds.
He was wearing a black and purple tuque and a black jacket and jeans when he disappeared.