Cause
The cause of the explosion was initially unknown. Some press coverage reported eyewitness accounts of gas industrial ovens in the coating department exploding. This has since been shown as unlikely as the gas ovens used on site have been found intact.
Another theory investigated by the Health and Safety Executive (HSE) was that there was no explosion. An article in the Scotsman newspaper of October 5, 2004 stated that the HSE was investigating the possibility that heavy machinery and pallets kept on the upper floors caused the floor to collapse, bringing the rest of the building down with it.
Other theories included a dust explosion and a build-up of methane beneath the building.
However the final inquest of the HSE indicated that the explosion was due to an ignition of gas released by a leak in a pressurised petroleum gas pipe.
The liquefied petroleum gas (LPG) tank and pipes that had been installed beneath the factory in the late 1960s had corroded allowing the gas to escape.
Read more about this topic: Stockline Plastics Factory Explosion