A fire broke out followed by an explosion of the gases formed (‘backdraft’ type) in a storage building of a fertiliser production plant storing raw materials (150 t of ammonium phosphate, 100 t of kieserite and 250 t of potassium sulphate), finished products (type C fertiliser, not capable of self-sustaining decomposition: 1,500 t of NPK 27-3-3, 100 t of P 26-6, etc.) and 500 t of NPK ‘off-spec’ fertiliser obtained during formulation development phases. The fire was controlled after 6 hours of fire fighting but the emergency services’ interventions lasted 15 hours in all. The storage building was destroyed and the site’s production was shut down for several days. The release of pollutants into the atmosphere (5 to 7 t of NOx, i.e. 10 to 13% of the annual authorised discharges) and into the water (22.7 t of nitrogen representing 25% of the annual authorised discharge and 710 kg of phosphorous) were significant but no human consequences were reported. Driven by the wind, the heavy fumes released were dispersed towards an uninhabited area. The causes of the accident were not clearly established as the installation was completely destroyed. Nevertheless, the accident was probably caused by heating of the fertiliser due to friction by the conveyor belt situated below the roof and operating when empty for over 2 hours. An electrical fault was also plausible. Furthermore, the build-up of NPK fertiliser dust in the building, conveyor belts made of combustible materials, the timber roof covered with tarred paper, the lack of a fire detection system in the storage area and the absence of fire walls in the conveyor belt tunnels were also aggravating factors. Gases from the fire and accumulating in the roof area exploded after the building’s dehumidifiers were switched on, thereby providing ‘fresh’ air (the moisture detected was caused by opening the storage area’s doors after activation of the alarms). The measures taken following this fire included: consultation with a specialist to secure the installation against fire, prohibition of operating equipment when empty, use of conveyor belts made from fire-proof materials, and improvement of the cleanliness of the installations, etc.