Friends, family and volunteers committed to finding missing 17-year-old Cooper Nemeth expanded their search Wednesday night to downtown Winnipeg.

Gateway Recreation Centre has become the search group's headquarters since Nemeth was reported missing four days ago. After searching the East and North Kildonan areas, as well as parts of East St. Paul, searchers fanned out across downtown Winnipeg.

Teresa Smith, who went to school with Cooper's father Brent Nemeth, has been helping out with the search.

"If it was my family, If I needed that type of help, I would certainly appreciate and need the foot power that we can provide," Smith said.

Nemeth's parents issued an emotional plea earlier Wednesday at a police news conference asking their son to "please come home."

RAW: Brent Nemeth makes heartfelt plea for son's safe return0:26

Samantha Kittner goes to school with Nemeth and also helped search Wednesday. Nemeth is a senior at River East Collegiate and plays centre for the River East Marauders hockey team.

"I just feel like everybody should do their part to try and find him," she said.

Possible witnesses

Police are looking for two potential witnesses — one named Brittany, one named Derek — they believe may have last seen Nemeth, who has been missing since the weekend.

Cooper James Nemeth

Cooper James Nemeth plays hockey for the River East Marauders. He was last seen early Sunday morning. (Supplied)

After playing in a hockey game on Saturday, Nemeth went to a friend's house on Amelia Crescent along with a 22-year-old man his aunt Laresa Sayles has said is known to police.

Nemeth and the man then went to a party in the Sun Valley area, according to police, and that's where the teen was last seen.

"​I can't just sit. I love this kid, you know? And I would absolutely do anything for him and I want to find him alive," Sayles said. "I'm not giving up, I can't. I can't until I know an answer."

Nemeth was diagnosed with ADHD, anxiety and depression in the past year. The family is concerned he has turned to drugs in an attempt to cope with his diagnoses.

He was last seen wearing a black jacket with a River East Marauders hockey logo on the front.

Police are asking anyone with information on his whereabouts to call 204-986-6250.