France, Sept. 12 -- The train, carrying 186 passengers between Rouen and Caen, came off the rails at around 7.45pm near the Renault factory in Cleon, south of Rouen.

A police source told reporters on Saturday that investigators had discovered a fragment of rail on the track and were treating the possibility of a deliberate act as the main line of inquiry.

The derailment prompted a major emergency response, with authorities activating a mass-casualty plan. Around 130 firefighters, five medical teams and 80 emergency vehicles were deployed to the scene.

Rouen public prosecutor Sebastien Gallois said 44 people had been injured, including an 18-year-old woman who was evacuated in a critical condition.

Tests carried out on the train driver...