The STM has some clues but still can't say what caused the problem that led to a partial shutdown of the orange line last weekend so the new Azur trains remain out of commission.
STM officials say the analysis shows so far that the problem is linked to a "lateral force" that resulted in the damage. They are ruling out a collision with anything on the track and any premature fatigue of equipment. The Polytechnique engineering school helped in the analysis.
But the STM still doesn't know if the train damaged the track or vice versa and can't say with certainty that it still isn't a problem with the new trains.
STM officials acknowledged that the issue of the part of the train coming into contact with the electrification of the rail previously existed and happened about "once a month" with less serious damage that did not warrant any further investigation.
The most recent incident led to part of the orange line being shut down for about ten hours last Saturday.
The STM says it will continue its night investigations and focus on where the "lateral force" is coming from: is it from the tight curves in the tunnel? Is it from the switching equipment?
Meantime the 13 new Azur trains remain parked and the next update is expected in a week.