Parks Canada officials said it took four days, a team of 28 people, a helicopter and an avalanche search dog to recover the bodies of three world-renowned climbers from an avalanche in the Rocky Mountains.

Austrian climbers Hansjörg Auer, 35, and David Lama, 28, and American Jess Roskelley, 36, summited Howse Peak around noon on April 16, after ascending a challenging route along the east face of the 3,200-metre-high mountain in Alberta's Banff National Park.

Anybody involved in an avalanche of that magnitude, it's going to be a bad outcome. - Brian Webster, Parks Canada

On Sunday, Parks Canada officials were able to recover the three bodies from the bottom of the 1,000-metre-high east face. It's believed they were in the process of rappelling down when a size 3 avalanche hit.

That's an avalanche strong enough to bury a car, break trees or destroy a small wood-framed building.

Parks Canada visitor safety manager Brian Webster said the route is considered extremely challenging.

"By all accounts these three climbers had the skillsets to climb this route. Having said that, anybody involved in an avalanche of that magnitude, it's going to be a bad outcome," he told reporters on Monday.

From left, Hansjörg Auer, David Lama and Jess Roskelley. (Facebook)

"There's no amount of skillset that's going to increase your ability to survive an avalanche like that."

The public avalanche bulletin on the day the climbers went missing rated the conditions as variable and subject to rapid change, Webster said.

"What is important to note here is that avalanche conditions changed significantly after the day of the accident … a significant storm rolled in and the hazard changed dramatically," he said.

Auer, Lama and Roskelley were reported overdue on Wednesday.

Howse Peak is remote, located in the northernmost corner of the park, and can only be accessed by skiing in.

Three experienced mountaineers were attempting the east face of Howse Peak in Banff National Park along the Icefields Parkway. (CBC)

Parks staff flew over the scene by helicopter, and saw "multiple avalanches and debris containing climbing equipment," the department said, at which point they presumed the climbers were dead.

They realized it wouldn't be safe to conduct a search and recovery effort on the ground, so they dropped an avalanche transceiver in the area from the air so they'd be able to find the site again.

Climbers weren't wearing beacons

None of the three climbers were wearing avalanche beacons, said Shelley Humphries, the Parks Canada official who oversaw rescue efforts.

She said while she understands that it's fairly common for climbers not to wear beacons, Parks Canada strongly recommends carrying the equipment if headed into the backcountry.

"In this particular case, the outcome would not have changed but it would have expedited the search and recovery," she said.

On Thursday and Friday, strong winds, snow and high avalanche conditions stalled the search. But on Saturday, safety teams were dropped in by helicopter, but stayed tethered to long-lines in case they needed to make a hasty exit in the event of another avalanche.

An avalanche search dog and handler were deployed by helicopter to locate the bodies of the three climbers killed in an avalanche on Howse Peak. (Parks Canada)

"Knowing we were going in for a recovery, it was not a rescue, we did not want to put rescuers in any danger," said Webster.

The teams started the slow work of probing the snow and ice to find the climbers' bodies. But, that search proved unsuccessful.

On Saturday, another hitch was thrown into the search. A second deadly avalanche happened that day, diverting teams to an avalanche near Lake Louise, Alta. A man was critically injured and airlifted to hospital, where he died the next day.

The search resumed on Sunday, four days after the climbers were reported missing. An avalanche search dog and her handler were sent in, also tethered by helicopter. The dog was able to find the climbers' bodies, and a recovery team was sent in to bring them home.

"We are relieved that this recovery has come to a safe and timely conclusion. Our thoughts are with the families and friends of those who lost their lives over the past week," Parks Canada said in an emailed statement.

All three athletes were professional mountaineers.

Roskelley was, in 2003, the youngest American to climb Mount Everest. He was 20 at the time.

Auer recently completed the first solo ascent of Lupghar Sar West, a remote 7,157-metre summit in Pakistan.

And Lama was part of a duo that made the first free ascent of the famous Compressor route on Cerro Torre in Patagonia, along the border between Argentina and Chile.

Condolences for the mountaineers' loved ones have poured in from the international climbing community.