At 5:00 p.m., a train derailed while on an industrial spur (private section of track that connects industrial sites to the national railway). Two wagons loaded with 57 tonnes of chlorine jumped the tracks, but remained standing on their wheels. A third wagon, which had only partially derailed, was put back on the tracks and taken away with the last wagon in the train (which contained 20 tonnes of a valeronitrile and hadn’t derailed). Emergency services personnel set up a safety cordon and the mayor closed traffic in the vicinity of the site. The entity in charge of managing the industrial spur (consisting of its user companies) had the wagons monitored by security guards.

The following day, three local families were evacuated and lodged in a hotel. The prefecture, firefighters, gendarmerie, managers of the industrial sites, and the entity managing the industrial spur held a telephone conference. They decided that the wagons would be raised using a system of hydraulic jacks having a thrust of 300 tonnes, placed back on the tracks, and taken away. The work began at 9:30 a.m. on 30 September, when the special hoisting equipment arrived by train from Bordeaux. Firefighters stood by with water nozzles all throughout. The work ended at 7:30 p.m. when the wagons were taken to a storage area to be shipped to their final destination. A specialist company replaced the damaged railway sleepers.

The derailment occurred at a turnout located along a curve. The railway company stated that trains are prohibited from travelling at more than 6 kph on these tracks and ruled out excessive speed as the cause. According to the media, the railway company, which was also responsible for inspecting the tracks on the site, stated that the last in-depth annual inspection of the tracks had not revealed any major problems. On 12 November 2008, two wagons loaded with vinyl acetate monomer had derailed on the very same industrial spur, releasing their explosive contents (see 35530). That accident had been caused by weakening of the track ballast. This accident, caused by the rails spreading apart as the train passed, occurred just after the train left the portion of track that had been repaired after the first accident.