Sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production and
Release of gases under pressure, or the
Release of gas under pressure. These high pressure gases then do mechanical work such as moving, changing, or shattering nearby materials.
I personally investigated this explosion/fire which blew the house off the foundation and burnt to the ground. The house was occupied at the time and how they got out is a miracle. A gas line was ruptured during excavation. The beautiful and historically home located right of the explosion home site was shifted almost a foot off it's foundation and had to be razed and rebuilt. Sad, it was gorgeous.
This was NOT Arson, this was simply a ruptured gas line caused by digging equipment. No more can be divulged about this case.