As police widen the area being searched Sunday in their effort to find Ariel Jeffrey Kouakou, a champion boxer has donated $15,000 to help find the missing 10-year-old boy who was last seen Monday afternoon.

Ariel had left his home in Montreal's Ahuntsic-Cartierville to walk to a friend's house when he went missing. His parents believe he was abducted.

After completing door-to-door and backyard alley searches within a 400-metre radius of where Ariel was last seen, police say they plan to expand the search perimeter.

"We want to give ourselves the highest chance and hope possible to find clues that progress the investigation," said police spokesperson Andrée-Anne Picard.

After completing door-to-door and backyard alley searches within a 400-metre radius of where Ariel was last seen, police say they plan to expand the search perimeter. (Radio-Canada)

A group of volunteers went door-to-door Sunday with photos of Ariel to see if they could get any new information about his disappearance. Many of them were parents.

"I think about this situation often. Obviously, it's not just Ariel. It happens every day. It's scary, especially when it's in your area," said Louise Neron, who was part of the search team, along with her husband and two children.

Mélanie Joly, federal heritage minister and MP for Montreal's Ahuntsic-Cartierville riding joined the group, saying "one of our children is missing."

She said that the search was under the purview of Montreal police, but "should there be any need for help, the federal government is there to support."

"This is a very important case," Joly said.

MP for Montreal's Ahuntsic-Cartierville riding, Mélanie Joly, joined the search Sunday. (CBC)

A command post remains in place at Galeries Normandie, a strip mall on de Salaberry Street in Cartierville.

"Information is coming in as we go," Picard said. "We are receiving tips from the public, but so far nothing that has moved our investigation forward."

So far, police are remaining open to hypotheses as to what happened to Ariel, as investigations are ongoing, she said.

Reward money boosted to $25,000

Champion Montreal boxer Adonis Stevenson has reached out to help Ariel's family, donating $15,000 in reward money.

This brings the total reward money to $25,000, since the family announced it would offer $10,000 to anyone with information on their son's whereabouts.

The boxer spoke at a news conference Sunday, encouraging people to share Ariel's photo on Facebook, Snapchat, Instagram and any other social media.

Adonis Stevenson met with Ariel's family on Sunday. (CBC)

He also called on anyone with any additional information on Ariel's whereabouts to call Info-Crime at (514) 393-1133.

"I have four children. It hurts my heart to imagine how this family feels," Stevenson said.

​He said he saw the parents' pain on television and assisted in the search for the 10-year-old.

Stevenson has held the WBC and lineal light-heavyweight titles since 2013.

Ariel went missing after he left his Ahuntsic-Cartierville home in Montreal early Monday afternoon. (Montreal police)

"We appreciate this gesture of positivity," said Ariel's father, Kouadio Frédéric Kouakou.

He thanked all Montrealers and especially Stevenson and his wife.

"I am dead sure [Ariel] will be back. It's not at random that we had this call this morning from the champion Adonis."

Read the latest on this search here.