Canadians Kam McLeod, 19, and Bryer Schmegelsky, 18, are sought in the murders of Australian Lucas Fowler and his American girlfriend, Chynna Deese.
The pair have also been charged with the second-degree murder of a third person, identified by police as Leonard Dyck.
All the victims were discovered in northern British Columbia earlier this month, but the suspects have now been tracked three provinces and hundreds of miles (kilometers) away to the northern Manitoba town of Gillam, police said.
The Royal Canadian Mounted Police have sent "a significant amount of resources" to the Gillam area, including tracker dogs, air surveillance, emergency response teams and crisis negotiators, spokeswoman Julie Courchaine said Thursday.
"We believe they are still in the area," Courchaine said, citing two separate sightings of the suspects in the Gillam area.
Television footage showed heavily armed officers in camouflage with dogs combing the woods and searching vehicles at road checkpoints.
In an interview with Canadian Press, Schmegelsky's father said his son was deeply troubled and "(wanted) his pain to end."
"He's on a suicide mission... he's going to be dead today or tomorrow," Alan Schmegelsky said of his son, explaining Bryer never recovered emotionally from his parents' divorce in 2005.
"Rest in peace, Bryer. I love you," said the older Schmegelsky, in tears.
"I'm so sorry all of this had to happen. I'm so sorry that I couldn't rescue you."
- 'Do not approach' -
The suspects were last spotted Monday before the federal police agency discovered their vehicle in the Gillam area. It had been set on fire.
Although the suspects had not been seen since, Courchaine added that there had been no vehicles reported stolen that could be attributed to the pair.
"Over the last 48 hours we have received over 80 tips and we continue to ask the public to remain vigilant," she said.
Public Safety Ralph Goodale echoed the sentiment during an event Thursday.
"Canadians can be in absolute confidence that every technique necessary to keep (them) safe is being applied in this case," he said.
Prior to the discovery on Monday of the burnt car, the suspects were last seen in the north of neighboring Saskatchewan province driving a gray Toyota RAV4.
The agency had earlier warned the public against interacting with McLeod and Schmegelsky.
"If you spot them - take no actions -- do not approach -- call 911 or your local police immediately," the RCMP said.
The Gillam area is "all swamp, heavy trees," and occasionally visited by polar bears, the town's mayor Dwayne Forman told public broadcaster CBC.
"There's only one road in and one road out," Forman said.
Police said the vast, densely forested area was hard to search.
"This is very challenging terrain," Courchaine said. "This is a large area, there's lots of dense bush, forest, swampy areas, so it is very challenging."
With wolves, bears and bugs to contend with, local guide Clint Sawchuck warned the hostile landscape was no place for the unprepared.
"It's scary being out in the bush if you don't know what you're doing," he told CBC News.
"You get off the beaten trail and it's all swamp, you're up to your waist in water.... and the bugs'd be eating you."
Initially considered missing, the RCMP said on Tuesday that McLeod and Schmegelsky were instead suspects in the shooting deaths of Fowler, 23, and Deese, 24, whose bodies were found on July 15.
Police later found the body of Dyck, believed to be in his 50s or 60s, about 300 miles (480 kilometers) away, near the ruins of a torched pick-up truck believed to have been used by the teen suspects.
Police think the man, described to officers as a "loving husband and father" by his family, was killed late last week.
AFP / Anthony WALLACE 
AFP /
AFP / Brendan Smialowski 
AFP / Brendan Smialowski