Around 6 pm, a gaseous release occurred at a potato transformation and preservation operation; the site was using hydrogen peroxide as a disinfectant and stored in a 1-m³ container within a case fitted with a retention. During a pipeline transfer, the product spilled inside the retention tank via a drain valve that had remained open. The product reacted with the tank lining, causing a temperature rise and the release of a vapour and peroxide cloud. Fire-fighters were called to the scene with 2 pumping vehicles and a ladder. The gendarmerie, town hall and Classified Facilities Inspectorate all visited the site. At 8:15 pm, the smoke release was stopped and the retention tank temperature was dropping. Company personnel continued to monitor the container every hour.

This scenario had not been foreseen in the safety report. The transfer pipeline drain valve had abnormally stayed open. Start-up of the transfer pump had not been preceded by verifying the state of repair of this valve. The inappropriate type of retention (relative to the peroxide) had been noticed. An alternative adapted retention had already been delivered, but its installation not yet performed.