At a steel mill, the melting of an initial basket of rebar in the main furnace was interrupted when emptying a second basket caused spattering of a much greater magnitude than usual. This spray, most likely containing slag, ignited small fire outbreaks, most of which could be quickly extinguished. The existing protection in front of the control room window panes and protection placed around the furnace the previous summer (recommendation issued in a safety report) successfully avoided exposure to individuals during the enclosure opening phase. However, an inspection hatch left open inside the enclosure leading to a service duct allowed this spattering to combust in the ducts running underneath the furnace control room. This fire partially destroyed this room. Fire-fighters, whose efforts were delayed due to cavitation of the pump supplying a fire hydrant from Seine River water, flooded the ducts with 200 m³ of water and foam (over 7 m³ of emulsifiers). Damage was estimated at more than €0.5 million and operating losses topped €1 million. Some 30 employees were made temporarily redundant for the 2 weeks needed to refurbish the control room and electrical ducts. The inspection authorities for classified facilities requested that the mill operator incorporate feedback from this accident into its safety report, notably by ensuring the successful operations of fire hydrants and expanding both duct protection and in-house first response resources.