Canadian police leading the manhunt for the suspected killers of Australian Lucas Fowler and his North Carolina girlfriend Chynna Deese have called in dive recovery teams to search a river.

Key points: Bryer Schmegelsky and Kam McLeod are triple murder suspects and have not been seen since July 23

Bryer Schmegelsky and Kam McLeod are triple murder suspects and have not been seen since July 23 Royal Canadian Mounted Police have called in dive teams to search a river near where their car was dumped

Royal Canadian Mounted Police have called in dive teams to search a river near where their car was dumped Survival experts predict the fugitive teenagers would struggle to survive in the wilderness around Gillam

The search for Bryer Schmegelsky, 18, and Kam McLeod, 19, has been going on for weeks, with authorities combing thousands of square kilometres for any sign of the fugitives.

They are suspects in the murders of Mr Fowler, 23, and Ms Deese, 24, who were found shot dead on the side of a highway in the western province of British Columbia (BC).

Kam McLeod and Bryer Schmegelsky had been on the run for nearly three weeks. ( Supplied: RCMP Manitoba )

Four days later, on another BC highway, the teenagers allegedly murdered botanist Leonard Dyck and then drove 3,000 kilometres east across Canada's north to the tiny town of Gillam, Manitoba.

On July 23 their stolen Toyota RAV4 was dumped outside of Gillam and set on fire.

There have been no confirmed sightings of the duo since.

The Royal Canadian Mounted Police (RCMP) announced on Saturday (local time) that underwater recovery teams were being called in to Gillam, with divers to begin searching the Nelson River on Sunday.

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'Significantly damaged' tinnie found

Canadian newspaper The Globe and Mail reported on Saturday night that a tinnie had been found along the shore of the Nelson River, spotted during a helicopter search.

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The paper quoted RCMP Inspector Leon Fiedler as saying it was not clear whether the tinnie was used by the two suspects.

"It had gone through some rapids and had been significantly damaged," Inspector Fiedler told The Globe and Mail.

"We're going to search in the area around where we found this boat just to make sure that there is nobody attached to it, whether that is our subjects or anyone else for that matter."

Despite unconfirmed sightings of the duo as far away as the neighbouring province of Ontario, the RCMP continues to search around Gillam.

However, Royal Canadian Air Force planes with infrared and other search technology have failed to find the fugitives in sweeps of the area.

Survival experts predict the teenagers would struggle to stay alive if they attempted to hide in the swampy, bug-infested wilderness around Gillam without shelter and equipment.

Canada has been gripped by the nationwide manhunt.

The Ontario Provincial Police (OPP) announced on Friday it had set up an investigative team to follow up on potential sightings of Schmegelsky and McLeod in that province.

The OPP received more than 30 tips in less than eight hours on Thursday.

The bodies of Lucas Fowler and Chynna Deese were found on July 15 along the Alaska Highway. ( Supplied: NSW Police )

Mr Fowler's father, Chief Inspector Stephen Fowler, told a Sydney memorial service on Friday that his son was living "a life that many of us envied" and he will "live on in our hearts".

Hundreds of the 23-year-old's family and friends gathered at the Uniting Church in Turramurra to honour his life.

ABC/AAP