What Caused the Giant Piper Alpha Oil Rig Explosion?

At 14,000 tons and 2.5 times the height of the Statue of Liberty, the Piper Alpha oil rig was one of the largest in the world. But on July 6, 1988, the entire structure became consumed by a devastating and deadly fire. From the show Make It Out Alive: Oil Rig Explosion: http://bit.ly/2xTAiqC