MONTREAL -- A helicopter circled overhead and dozens of law enforcement and volunteers canvassed a Montreal neighbourhood Thursday as police assured the public they were doing everything they could to find a missing 10-year-old boy.

Police could be seen going door-to-door, speaking with residents and looking into recycling bins and under porches as groups of citizen volunteers handed out flyers to passersby.

Montreal police spokesman Jean-Pierre Brabant said authorities still don't know what happened to Ariel Jeffrey Kouakou, who hasn't been seen since Monday.

Officers in boats and on horseback combed a river and a wooded riverside park where Kouakou was last seen by a witness shortly after he left his family home to head to a friend's house, he said.

More than 120 tips have been called in since police launched an Amber Alert for several hours Tuesday, but Brabant said none of them have proved concrete.

"For now, all the hypotheses are looked at because we don't have any leads," he said in an interview.

"We have more than 100 tips that came into our line and all of them were looked at, but none of those helped us to start a point of search."

The boy's father, Frederic Kouakou, told reporters he is convinced the boy was kidnapped, and he appealed to anyone with information to come forward.

Yannick Adou, one of several dozen volunteers who was helping in the search, said he too believes the boy was abducted, adding the group would be going door-to-door to find out if Kouakou is in someone's home.

Adou, who knows the Kouakou family, said the disappearance of one of the community's children was felt by everyone.

"I'm a father, I have three kids, so it's painful to know that we lost one of our kids," he said.

"We are mobilized to find Ariel, and it's very, very important for all of us."

Another volunteer, Sandra St-Amour, said she didn't know the family but, as a mother, was moved by their plight.

"When a kid is missing, everybody should come give a hand because it could be your kid, you never know," she said.

Const. Raphael Bergeron says officers patrolled the north-end Montreal neighbourhood during the night but saw no sign of Kouakou.

Police say the boy, who is French-speaking, is black, has black hair and black eyes and was wearing a black coat with a hood, grey pants and yellow shoes before he disappeared.

A mobile command post remains in the area and authorities are asking anyone with information to call police.

Brabant admitted the search was becoming harder with each passing day but said police won't give up until the boy is found.

"It's quite rare (in the case of) a young boy who has been missing for three days in a residential neighbourhood for nobody to see anything," he said.