Police have been searching more than a week for Kam McLeod, 19, and Bryer Schmegelsky, 18.
A “credible tip” of a sighting has led police to refocus their search around the community of York Landing.
The sighting is believed to be the first in several days of Mr Schmegelsky and Mr McLeod.
Members of the indigenous-led Bear Clan Patrol, a community safety organisation based in Winnipeg, spotted two men on Sunday they believe are the pair.
Searchers had spent most of the past week looking for the suspects near the community of Gillam, Manitoba.
York Landing is accessible only by air or, in the summer, a ferry from Gillam.
The town’s roughly 500 residents have been warned to remain vigilant and stay locked indoors “as much as possible” and to immediately report anything suspicious.
Police say their current goal is to safely locate and apprehend the individuals and confirm their identities.
The search has been hampered by a challenging terrain with expanses of forest, bogland and waterways.
Canada’s military has pledged air support to assist the manhunt.
What do we know about the suspects?
Mr McLeod and Mr Schmegelsky, both from Vancouver Island, had been on their way to Yukon territory for work this month.
The pair were initially considered missing, but on 23 July police named them as suspects in the deaths of Chynna Deese, a 24-year-old American, and her Australian boyfriend, Lucas Fowler, 23. No charges have yet been laid in that case
Police have charged Mr Schmegelsky and Mr McLeod with second-degree murder in the death of Leonard Dyck, 64.
The two were considered “armed and dangerous” and the public have been warned not to approach them.
What do we know about the victims?
Lucas Fowler and Chynna Deese were killed sometime between 14 July and early 15 July. Their bodies were found 12 miles (20km) south of Liard Hot Springs along the Alaska Highway.
They were on a two-week-long road trip across Canada and Mr Fowler had been working in the country.
A statement released by the Fowler family said they had lost a “son, brother, grandson and friend in the most terrible of circumstances”.
Leonard Dyck was found dead on 19 July, near Dease Lake.
He was a described as a loving husband and father as well as a “cherished” botany lecturer at the University of British Columbia.