At 6:40 am, a road tanker containing 12 m³ of liquefied propane under 8 bar of pressure struck the gate of a filling centre. A leak ensued on the cistern around the drain downstream of the distribution pump (diameter: 12 mm), housed in the right side compartment in back of the lorry. Ripping the compartment off its support caused bursting of the drain located between the bottom flap and the closure valve. The flap, which was at least partially open, was unable to provide a seal. The centre’s manager activated the site’s shutdown procedure and triggered the internal emergency plan. The 3 individuals present onsite used (3) sprinkling hoses connected to fire hydrants to both limit spread of the gas layer and form an ice plug. Fire-fighters took over these operations upon their arrival and installed 1 turret nozzle and 3 smaller protective nozzles. At 9:30 am, the lorry was completely drained using a flare set up 50 m away to continuously burn the released gas. Around 11 am, an ice plug formed and clogged the leak. It was then attempted to close the bottom flap, but in the presence of pressure the ice plug broke and leaking resumed. After several subsequent attempts and with 22% of the propane still left in the cistern, the bottom flap could be freed and closed. The cistern was once again fully sealed. A mechanical plug was placed on the pipe. This accident had caused the discharge of 4 tonnes of propane into the atmosphere. The intervention was wrapped up around 12:30 pm. The cistern was then emptied and inerted. The Classified Facilities Inspectorate recorded the facts and requested a detailed incident report from the operator, along with a determination of its precise causes and an explanation of how this incident had been or would be included in site safety reports. According to initial investigation findings, the lorry driver activated the digital access code on the automatic gate, which consisted of 2 leaves opening inward, but did not wait for the gate to open entirely. He stopped 7 or 8 m further after noticing the leak. The bottom flap was appraised: a defective actuator on this device was highly suspected.