Investigators believe the train that derailed near the B.C.-Alberta border on Monday, killing all three crew members on board, started moving on its own shortly before the accident.

Canadian Pacific train 301 had been stopped at a station for about two hours with its air brakes applied when it suddenly began accelerating, the Transportation Safety Board said Tuesday.

"It was not anything the crew did," senior investigator James Carmichael told reporters.

"At this point we're calling it a loss of control, which is when the crew can no longer maintain the track speed."

The grain train had been parked at Partridge, the last station before the Upper Spiral Tunnel, for a shift change because the previous crew was reaching their maximum hours of service.

That's when conductor Dylan Paradis, engineer Andrew Dockrell and trainee Daniel Waldenberger-Bulmer boarded to continue the train's westward journey to Vancouver.

Carmichael said the new crew wasn't prepared to leave when the train started moving.

"They were on board but there are things that have to take place before they leave – they have to do their checks and make sure that their paperwork is in place before they depart," he said.

Investigators haven't determined what caused the brakes to apparently release, but said the train began accelerating "well in excess" of the 32 km/h limit for the steep and bending tracks in the area.

The deadly derailment began when the train hit a curve before a bridge, sending 99 cars and two locomotives plunging more than 60 metres down onto an embankment. The lead locomotive came to a rest in the Kicking Horse River.

Just 13 cars and the rear locomotive remained on the track after the accident.

The CP crew members' names were released hours later, leading to an outpouring of grief from their friends and family.

Waldenberger-Bulmer's father shared a heartbreaking Facebook post describing his 26-year-old son as a man who shared his love for adventure.

"I am sad to report that I have lost one of the jewels in my crown last night in a tragic accident," he wrote. "Rest in peace my dear man."

CP Rail president Keith Creel issued a statement Monday afternoon saying the company is working closely with the deceased crew members' families and with all of its employees as they process what happened.

"This is a tragedy that will have a long-lasting impact on our family of railroaders," Creel said in a statement.

"To all those who have offered their thoughts and prayers – thank you. As we work to safely recover from this tragedy, we do so with our fallen colleagues in mind."

A GoFundMe has been set up for the victims' families, and had already raised more than $27,000 by Tuesday afternoon.

CP Rail said it's also working with Parks Canada to ensure the environment isn't negatively affected as it begins the difficult process of removing the wreckage from the remote location.

The Transportation Safety Board said investigators’ next steps will be to recover the event recorder data from the lead locomotive, which was severely damaged in the accident, and obtain whatever data they can.

The TSB is tasked with investigating marine, pipeline, railway and aviation accidents, with the aim of improving public safety. It does not assign blame or determine civil or criminal liability.

Other agencies, including Transport Canada, Employment and the BC Coroners Office, are also conducting concurrent investigations into the derailment.