A train derailed at 2:56 am at the Lausanne rail station; 7 of the 50 cars on this 690-m (1,753-tonne) convoy were on their side on the track. Two cars transporting a total of 80,000 litres of epichlorohydrin leaked, allowing 400 litres of a toxic, volatile and flammable chemical product to escape.

The alarm was sounded at 3:14 am, with over 500 fire-fighters arriving at the scene to: plug the car openings, recover the product that had spread, and ventilate the sewers. The entire district, accounting for 1,500 residents, was evacuated as a safety measure during the emergency response. No injuries were reported. Over the ensuing 4 days, the tanks of both epichlorohydrin and thionyl chloride were emptied, the overturned cars were placed upright, discharged or returned to their recipients. The local population would have to be evacuated a second time when performing hazardous operations (e.g. standing the cars upright).

The accident was caused by a switching error. The train entered the station on track no. 3. When it crossed onto switch 76a, on the eastern side of the station, the 25th railcar (which was rolling empty on its 2 axles rose, then fell adjacent to the tracks and stayed on its path by rolling along the railroad ties, while being supported by the platform edge. The train was making a service stop at the station in order to rotate conductors; however, upon restarting the convoy, the wheels on the derailed car remained trapped between the rail and the platform edge. At the end of the platform, in the track switching zone, the 2 cars preceding the empty car, along with the 11 subsequent cars, derailed. Of these 14 cars that left the rails either totally or partially, 5 of them, including 3 tanker cars containing hazardous freight, were lying sideways on the track. The one was transporting thionyl chloride and the other 2 epichlorohydrin. The first epichlorohydrin tank was slightly punctured, which caused the contents to flow out. The cars containing hazardous substances damaged in the accident carried respective capacities of 47,000 litres of epichlorohydrin and 24,000 litres of thionyl chloride.