Winnipeg | Reuters — A Canadian Pacific Railway train was parked for a change of crew when it unexpectedly rolled down a steep embankment and derailed in British Columbia’s Rocky Mountains on Monday, killing three crew members, a transport regulator said.

The train, hauling 112 cars of grain, was parked for two hours at the last station before a tunnel near Field, B.C., to allow a new crew to replace one that was near its maximum hours of service, Transportation Safety Board (TSB) senior investigator James Carmichael said on Tuesday.

He said emergency air brakes were applied before three crew members, a locomotive engineer, conductor and conductor trainee, boarded the train and prepared to depart for Vancouver.

The train then “began to move on its own,” exceeding its maximum track speed of 20 miles per hour (32 km/h) for the tight curves and steep mountain grade, and derailed, Carmichael said.

The area features some of the most challenging terrain for trains in North America, he said.

CP could not be immediately reached. On Monday, CP CEO Keith Creel said in a statement that the company would not speculate on a possible cause.

Carmichael said the TSB’s investigation would continue to determine how the loss of control happened.

TSB representatives haven’t yet spoken to the train’s previous crew as to whether it had any problems before the new crew boarded, he said.

Apart from the 112 hopper cars, the train also included three locomotives at the front, middle and rear, the TSB said.

The lead locomotive and some of the cars derailed on a curve prior to a bridge, the TSB said, where the lead locomotive came to rest on its side in a creek and a number of derailed cars came to rest on an embankment.

Many of the remaining cars, including the mid-train remote locomotive, piled up behind them, and only 13 cars and the rear locomotive remained on the track, the TSB said.

Event recorder data from the “severely damaged” lead locomotive hasn’t yet been obtained, the TSB said, while some data has been recovered from the tail-end remote locomotive and “work is underway” to get data from the mid-train remote locomotive.

Eight railway workers have died in Canada since November 2017, including Monday’s deaths, according to the Teamsters union that represents Canadian rail workers.

— Reporting for Reuters by Rod Nickel in Winnipeg. Includes files from Glacier FarmMedia Network staff.