On 26 June, an external company was working to connect 2 storage tanks to the fillers of 2 lines at a plant manufacturing household products. Before starting the work, a prevention plan and hot work permit were issued for the subcontracted workers. Two of the subcontracted company’s employees were cutting and welding pipes. The first tank was drained and its valve was closed. At around 10 am on 29 June, when disconnecting the pipework, liquid spilled on to the ground, forming a puddle. Although the nature of the fluid was not identified, one of the workers cut the pipe in the presence of his colleague equipped with a powder extinguisher. When the latter left, one of the workers raised up the pipe and started to weld. The first worker felt heat on his back 5 minutes later and noticed blue flames: the spilled liquid had ignited. The employees present in the filling area and in the R&D laboratory raised the alarm. The staff evacuated the premises while 3 employees controlled the fire with a powder extinguisher, a CO2 extinguisher and the first aid hose system. The spilled liquid, which was a semi-finished product, was a bactericide containing 80% ethanol. The sparks that fell on the puddle of liquid during the cutting were not sufficient to start the fire, but the increase in temperature due to the welding had ignited the alcohol vapours released by the puddle. During an inspection, the inspection authorities for classified facilities noted that sections of the hot work permit had not been filled in correctly, that the pipe had not been properly drained before the work, that the employees had continued to work without knowing the nature of the spilled product and without notifying one of the company’s managers. It was recommended that the Prefect issue a formal notification order.