In an oil depot, an explosion followed by a fire occurred at 10.15 am on a 500 m³ empty tank (no. 1802), during the reheating phase before filling with additive-treated bitumen. The intervention, which mobilised 60 firefighters and 16 fire engines, ended at 11.45 am and the operator implemented suitable safety and monitoring systems. The projected roof of the tank fell a few meters away between the full tanks no. 1801 and 1803 which were identical to the tank affected and were installed in the same retention system. The liquid waste recovered (extinguishing effluents, cleaning effluents and oils) was pumped, then eliminated. The solid waste was gathered on the site pending subsequent disposal. No water pollution was noted in the RHONE river or in the neighbouring stream. There were no victims and the material damage was limited to tank no. 1802. The two neighbouring tanks and pipes of the system were not damaged. Gas sampling taken close to the affected tank showed no abnormal concentration of VOC and H2S. The tank, which had not been used since June 2005, had been cleaned with very low sulphur content heavy fuel oil in January 2006. The work undertaken for approximately 2 months to replace the thermal insulation, had finished on the afternoon of 24 March with closure of the manholes and start up that very same evening of the reheating system, consisting of two circular coil heaters containing oil-type coolant, heated to 210°C. The inspection authorities for classified facilities drew up reports establishing the facts. On 31 March, the inspection service of the neighbouring refinery proposed procedures for putting the 2 neighbouring tanks back in operation without causing significant damage. The preferred hypothesis was ignition of hydrocarbon vapours that had desorbed and/or cracked due to the increase in temperature in the tank’s atmosphere, due to incandescent pyrophoric compounds formed in the presence of sulphur compounds activated by the air circulating between the roof’s vent and a 2-inch branch pipe left open following dismantling of a sampling valve.