Two teenagers, Kam McLeod, 19, and Bryer Schmegelsky, 18, are wanted in connection with the deaths of American Chynna Deese and her Australian boyfriend Lucas Fowler, as well as an unidentified man in his 50s or 60s.
Ms Deese, 19, and Mr Fowler, 23, were found shot dead on 15 July along the Alaska Highway about 12 miles (20km) south of Liard River Hot Springs, a popular tourist spot, in northern British Columbia.
Both deaths appear “suspicious”, but the investigation is still “in its very infancy”, police said.
McLeod and Schmegelsky were initially considered missing persons after their burning truck was discovered on Friday near the town of Dease Lake, almost 311 miles (500km) south on the same road.
Sergeant Janelle Shoihet said: “The Royal Canadian Mounted Police are now considering Kam McLeod and Bryer Schmegelsky suspects in the Dease Lake suspicious death and the double homicide of Lucas Fowler and Chynna Deese.”
The pair have now left British Columbia and have been travelling in northern Saskatchewan in a grey 2011 Toyota Rav 4, police said, saying they are considered dangerous and should not be approached.
McLeod and Schmegelsky, both of Port Alberni, British Columbia, were travelling to Whitehorse in the Yukon to look for work and had not been in contact with their families for the past few days.
Police are still working to identify the man found dead roughly a mile from the vehicle, but said he appeared to be in his 50s or 60s.
They released a sketch of a man with a heavy build with a grey beard and grey hair, and asked for public help in identifying him.
On Tuesday, they released CCTV images of Deese and Fowler at a petrol station.
Fowler, the son of a chief inspector with the New South Wales Police Department, was living in British Columbia and Ms Deese was visiting him.
They were on a two-week-long road trip across Canada, where Mr Fowler had been working.
The two were going to travel in a van through Canada to visit all the national parks, according to Sheila Deese, Ms Deese’s mother.
“They had mapped out their route. And to my understanding, the van broke down and that’s where tragedy happened.
“They had plans for the future. They were meant to be. She loved him very much.”
Mr Fowler’s family said they would travel to Canada to “be with our boy and to bring him home”.
“To lose someone so young and vibrant, who was travelling the world and just enjoying life to the full, is devastating,” their statement said.