Dufour confirmed that CN had recently performed maintenance at the Bourg-Neuf Boulevard level crossing where the derailment took place.
He said the cause remains unknown and that the city will continue questioning CN and the federal government.
Provincial Environment Minister and Repentigny MNA Pascale Déry commended local responders for their swift actions.
Repentigny Police spokesperson Bruno Marier said no residential structural damage occurred despite the proximity of backyards to the tracks.
He added that a federal agency will likely investigate.
CN spokesperson Ashley Michnowski initially reported about 20 cars derailed, later updated to 45. No leaks, fire, or injuries were reported.
Investigators remain on site to determine the cause.
Repentigny Fire Department Deputy Chief Jean-Marc Picotte confirmed the first emergency call at 4:33 p. m.
He noted that six cars containing hazardous substances remained on the tracks, while three derailed tankers previously used for diesel were empty.
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The derailment knocked down overhead power lines, causing localized preventive blackouts in two city sectors.
