The News Tribune posted a surveillance video from the site of the Atlas Foundry explosion two weekends ago. In it you can see the truck begin fuming white gas and eventually ignite. Here's a sequence of screens from the video:
Also, in case you didn't hear, I'm sad to say the driver of that truck did not survive. It's amazing he was the only one. I even heard a 3rd-hand story about an Atlas employee who pretty much saved about 30 co-workers when he noticed the gas leaking into a building near the truck and got everyone out.