Just hours before a Via Rail train derailed in Saskatchewan last year, inspectors had examined the track and decided it was OK, a Transportation Safety Board report on the April 28 accident says.
However, it turned out the roadbed at the Togo location near the border with Manitoba had been weakened by melting snow and some of the material underneath one section of tracks had been washed out.
When the Via Rail passenger train went over the section, four hours after the inspection, members of the train crew could see some of the material was missing.
The brakes were applied, but the train couldn't stop in time.
"As the train passed over this location, the embankment further collapsed causing the two locomotives, a baggage car and the first passenger car to derail upright," Transportation Safety Board said Wednesday in a news release.
The diesel tanks were ruptured and the train caught on fire, with both locomotives being damaged. The fire was put out and no one was injured. The Via crew and passengers were evacuated from the train.
The report found that the root cause of the washout was a blocked culvert combined with a rapid melt of snow, which led to ground being saturated and the embankment weakened.
It also noted that the track inspectors responsible for the location had not received "any significant training" in identifying potential ground hazards.
"Without such training, track inspectors may not detect unstable ground conditions in a timely manner, increasing the risk of a derailment," the TSB said.
Following the derailment, CN produced a video and other training materials to help inspectors look for embankment problems during the spring runoff period.