At 9:30 am, a certified delivery driver entered an industrial gas plant. Five minutes later, he drove his light-duty utility vehicle inside a closed hangar used to fill inert gas bottles under pressure. His vehicle contained flammable and combustive gas bottles from outside the site boundary and opened by the driver prior to entering the hangar. The explosive atmosphere created inside the vehicle combusted when making contact with an unidentified ignition source. Pieces of the vehicle’s interior compartment, blasted during the explosion, struck parts of the building roof and siding as well as some of the production machinery.

Notified by plant security agents, fire-fighters from a nearby fire station arrived at the scene in less than 10 minutes. While surveying the explosion site, they caught the driver in the process of manually opening the valves on industrial gas bottles stored both inside the building (inert gas) and outside (flammable gas). Two responders chased him down and neutralised him. During the action, one of them sustained slight injuries to the arm. Flames were seen spewing from the valves of two flammable gas bottles, which were immediately closed. Fire-fighters and plant personnel stopped all leaks by closing the valves on other open bottles and locking down the installation.

Plant employees were evacuated, while personnel with firms in the vicinity were confined to their sites as police forces secured the entire industrial zone. The crisis unit assembled by emergency responders initiated treatment of trauma sufferers. It should be noted that no employees sustained physical injuries.

The investigation was assigned to the anti-terrorism prosecutor’s department. The “Vigipirate” alert system was raised to “attack alert” for 3 days in the Rhone-Alps Region. Safety measures were reinforced across all of France’s Seveso sites.