There are several different witness reports as to the events directly preceding the blast, all of which are more or less equally plausible. Some reported the tank was already leaking as it approached the site, or sprang a leak with a loud bang while passing the site, and was then stopped by the driver. Others reported the bang being caused by a blown tire which caused the truck to swerve out of control and crash into the wall separating the campsite from the roadside, possibly overturning in the process.