Boaters with the group Drag the Red started combing the riverbed late in the afternoon, while other volunteers searched along the riverbanks earlier in the day.
But Bernadette Smith, who spearheaded the Drag the Red initiative, said some volunteers have been searching longer.
"We were told it's like looking for a needle in a haystack when there's no needle," she told CBC News.
The search boats are drifting down the river, motors turned off. Each has a metal bar, with four hooks attached, suspended about four metres underwater.
"If we do find something … we just put a buoy there, mark it, and we just get out of there and let the police handle it from there," said Calvin Alexander, a volunteer.
A shopping cart and a large hose were among several items pulled out of the river on Wednesday evening.
Searchers dragged the river until about 7:30 p.m. CT. The group plans to resume on Thursday.
Some volunteers said they'll remain at the search site every day until the Red River freezes.
'It just breaks my heart'
The Drag the Red project was initiated by Smith, who has been searching for her sister, Claudette Osborne, since she went missing in 2008.
Smith said the idea was prompted after the body of 15-year-old Tina Fontaine was found in a bag in the Red River near Alexander Docks in August.
"When Tina Fontaine was found in the river, I put a post on Facebook saying that the river needs to be dragged. Kyle Kematch, who is also searching for his sister, said, 'Let's do it' and a community member from Ontario — Percy Ningewance — came forward said, 'I'll help with the drag. I've done it before,'" she said.
A number of people, including family members of missing and murdered women in Manitoba, gathered along the riverbank as the search got underway.
Brittany Spence, 16, says her parents told her she's too young to search the river, so she's maintaining a fire near the Alexander Docks and supporting her family.
"Just in case that we do find a body or something, they don't want me to see anything like that," she said earlier on Wednesday. "But I'm just trying to help as much as I can."
Spence's aunt, Sandra Murray, vanished into the river last week. She has been battling depression, according to family members.
"I thought she was the only one that went missing until I got down here and talked to the elders and everyone," Spence said. "There were a lot of missing aboriginal women down here, and it just breaks my heart."
Bones, other items found in river
Kyle Kematch, who helped start Drag the Red, has many reasons to be part of the search: his youngest sister, Amber Guiboche, is missing.
Guiboche was 20 when she was last seen in November 2010 in the William Avenue and Isabel Street area in Winnipeg.
Kematch said Drag the Red searchers found other items during test drags of the water and by walking the riverbank; including dentures, a stained pillow case, a large mat and objects that appeared to be bones.
It hasn't been determined if they are bones, human or not. Smith said Winnipeg police told her the specimen has been sent to a laboratory in Ottawa for analysis.
It could take up to six weeks to get the results, she said.
The mat was recently pulled out near the Alexander Docks, the same place where 15-year-old Tina Fontaine's body was found in August.
"When I got to the dock, [the mat] was rolled out. It looked like there was blood stains on it," Kematch said.
"I'm not a forensic guy, but that's what I would automatically assume because it looked like the same exact colour that was on the pillow case."
Kematch said finding those items already makes him feel justified for helping start the Drag the Red project.
"That's what I make of it — we're getting somewhere because we're pulling up stuff," he said. "It's just weird and good at the same time, so I do feel like it's, it's giving me answers. I was wondering before if there is anything in there."
Police to be on river
Winnipeg police plan to be on the Red River on Wednesday afternoon as volunteers drag it.
Spokesman Const. Jason Michalyshen said the police service supports the search "wholeheartedly" and will work closely with the volunteers.
"I can't stress enough how we do applaud the efforts of the organizers and the people directly involved. I think Winnipeg, not only the city, the province, nationwide, they want answers, they want resolution," he said.
However, police will not drag the river themselves.
Two members of the police river patrol will be present in a boat to monitor the efforts of the volunteers and collect any found items, as well as to make sure searchers stay safe.
Grand chief helps search
The Assembly of Manitoba Chiefs joined searchers on Wednesday afternoon, with Grand Chief Derek Nepinak and two AMC staff members launching a search boat.
"It is important that we focus on the good hearts of the people that are demonstrating their love for our people and our community in this effort. We cannot focus all of our energy on chasing governments who are not willing to take appropriate steps towards resolution and closure for our families," Nepinak said in a statement.
"To focus on the immediate needs of an inquiry into the unknowns, which this effort on the Red River is, we are demonstrating that inquiries into the fate of our murdered and missing loved ones need not be viewed as academic or political exercises, but rather real efforts by people to bring immediate tangible outcomes for the health of our families and community. It is on this basis that I fully support this community-driven initiative.
"Furthermore, I would encourage other families and communities living in the cities across the country to organize similar efforts to search for their missing loved ones, because its going to have to be us who do this, no one else will," he added.