The vapour cloud was noticed by members of the public off site and by tanker
drivers on site waiting to fill their vehicles. They alerted employees on site. The fire
alarm button was pressed at 0601 hrs, which sounded the alarm and started the
firewater pump. A ‘vapour cloud explosion’ occurred almost immediately, probably
ignited by a spark caused by the firewater pump starting. By the time the explosion
occurred, over 250 000 litres of petrol had escaped from the tank.