While workers are injecting concrete to reinforce a sewer on behalf of the equipment service, an explosion and fire occur when they perforate the side wall. Two workers are severely burned and curls of black smoke escape through the sewer outlets over a 1.5 km stretch of the pipeline. The area within a radius of 200 metres is demarcated as a danger zone, and traffic is stopped in both directions on the RN2 national road. Some of the offices and restaurants located in the accident zone are evacuated. The emergency response mobilises more than 80 fire fighters and 20 specialised machines for 7 hours; the damaged sewer is inundated with foam. The causes and circumstances of the accident remain undetermined. Explosivity measurements are taken throughout the night and a fire fighting plan is kept in effect in case the fire reignites. The accident appears to have been caused by a pocket of pollution with a high concentration of flammable liquids, following the discharge of hydrocarbons into the sewer when its wall was perforated; a petrol station that has long been out of service is located nearby. A criminal investigation is conducted with the help of the central forensic laboratory. Given that the water trap passed through the water table, the water is pumped out the next day in order to locate the leak and attempt to stop it. Four days later, the water trap is once again filled with foam after explosivity measurements again show dangerous concentrations of fuel vapours. On 5 February, a specialised company brings in divers to detect and stop the fuel leaks. The accepted hypothesis is that when the petrol station was in service, there was a constant leak which stagnated as it reached the first impermeable layers. On 20 March, a series of bore holes are drilled in the ground at the old petrol station in order to locate any traces of hydrocarbons. The 5 sample borings reveal the presence of petrol and diesel in the first layers of the water table. A very large quantity of water – some discharged by the emergency responders but mostly seepage water – is polluted by the hydrocarbons present, though at a low concentration. The polluted water is pumped out and discharged into a neighbouring water trap.