A tanker truck containing 19 tons of ammonia (NH3) burst open during an unloading operation. A toxic cloud (1.5 km long, 150 to 400 m across, with wind blowing at 1 m/s and fog observed over the first 300 to 400 meters) surprised employees exiting the cafeteria. The front of the tank and the tractor-trailer were propelled 26 m by the gas pressure release and crashed through a 22-cm wall of a disused workshop before being stopped by a second wall. The back of the tank was held in place by piping running through the plant. The driver and two plant workers were killed instantly, and 7 other employees (3 of whom died in the days following) and 20 local residents were hospitalised. The tank’s baffle plates were found some 25 to 30 m from the site of the explosion. The rupture, which caused the accident, was tangent to an weld bead of an internal iron support on which one of the tanker’s baffle plates was mounted. Another internal weld bead showed signs of a weld executed after a rather primitive assembly, subsequent to a repair performed on the tank that had been deformed by an impact which occurred 2 or 3 years earlier. The accident was due to corrosion under stress exposure (high-resistance T1 steel + NH3 + stresses).