A transformer exploded and ignited at 10:15 am, causing projections around the room and an oil spill that partially flowed into the municipal sewage network via gutters. Neighbours notified local fire-fighters, who were on the scene by 10:30 with their standard emergency equipment. A CMIC unit specialised in chemical emergencies had the fire under control 10 min later using a powder extinguisher. Rescue crews noted the presence of oil on the pavement and in a storm drain manhole that was poorly maintained and clogged; since a risk of overflow was feared, another CMIC unit called in as a backup pumped 50 litres of oil into the manhole. As opposed to the first agents onsite at 11:05, the electricity distribution team did not confirm the presence of PCB in the device that had been operating since 1965. Samples were extracted for analysis, the site was cleaned, and the emergency intervention officially ended at 1:10 pm. For precautionary reasons, doctors examined 15 fire-fighters, 2 witnesses and 2 gendarmes, despite showing no symptoms. A blood test was also administered to each of them the next morning. The presence of PCB was finally confirmed upon the Hazardous Installation inspection at 5:30 pm; the oil contained 89 g/kg of PCB, i.e. a concentration greatly in excess of 50 mg/kg and necessitating the decontamination of equipment. The pumped oil and polluted wastes were transferred and isolated at an appropriate site. In order to prevent against additional pollution tied to PCB, a strip of soil hit by oil spatter was scraped 20 cm deep with transfer onto the same site as the excavated earth and transformer. On July 16, the electricity distribution service performed additional sampling of the polluted pavement surfacing before having it covered with a tarp, while informing the IIC Office of the discovery of an unauthorised white verification tag on the transformer (a yellow tag indicates PCB content, a green one content free), dated 2001 indicating the possible presence of PCB. At IIC’s request, dioxin analyses of the soot were carried out on July 17. Since the presence of PCB was unknown at the time of the accident (poor communication between fire-fighters and the site operator), the emergency crews did not take all the effective precautions during their performance onsite: cleaning water discharged into the network, crew members not equipped with adapted protective gear, individuals present on the site (police, neighbours) not removed or evacuated accordingly. Once the presence of PCB had been established, all those exposed to fire smoke received proper care and were placed under medical observation.