Kam McLeod and Bryer Schmegelsky have been missing since July 19

Two teenagers, first categorized as missing in Canada, are now suspects in the murder of an Australian tourist, his American girlfriend and an unidentified man whose body was found near the teens' abandoned, flaming car, police said on Tuesday.

Lucas Fowler, 23, an Australian citizen, and Chynna Deese, 24, from Charlotte, North Carolina, were found shot dead on July 15 on a highway in northern British Columbia, 20 km from Liard Hot Springs.

Kam McLeod, 19, and Bryer Schmegelsky, 18, have been missing since July 19. Their car was found in flames about 500 km away from where Fowler and Deese were found dead, near Dease Lake, British Columbia.

The body of a man the Royal Canadian Mounted Police (RCMP) are still trying to identify was found 2 km from the abandoned car. It was not immediately clear to police whether the body was connected to the car and the missing teenagers, but the RCMP said they are now also considering McLeod and Schmegelsky as suspects in the man's murder.

McLeod and Schmegelsky were last seen in northern Saskatchewan, driving a grey 2011 Toyota RAV4, the RCMP said.

The Australian Broadcasting Corporation (ABC) was interviewing Deese's mother, Sheila, when police announced that the teenagers were suspects and warned the public not to approach them, instead saying to call 911.

"I need for anyone with information to share that, because this can't happen to another family," the mother was quoted as saying.

"It shouldn't have happened to ours."

Lucas Fowler, 23, an Australian citizen, and Chynna Deese, 24, from Charlotte, North Carolina, were found shot dead on July 15 on a highway in northern British Columbia

Police have cited the vastness of the area in question, as well as its remoteness, as factors complicating their investigation.

It is not known if McLeod and Schmegelsky are armed, or what their motives may be. The ABC said Deese was due home on July 31, with the day marked "Chynna returns" in the calendar by the kitchen at the family's North Carolina home.

"I don't know what I'm going to do on July 31," Sheila told the network. "Chynna was a sunflower. Strong and tall and beautiful."