We used to have an experiment in high school, where a relatively small amount of coal dust, was placed in a container, and then by blowing through a hose, that coal dust was dispersed into the air inside of the container, then a flame, from a lit match, was then touched to that dust, and it would result in an explosion. This is the same kind of the dust explosions that are so well known in the graineries, and silos, of the midwest.
When you have so much fuel, the chance of an explosion, and fire, is very high. All that is required is that spark to cause ignition.
With the very high price of coal, there is a rebirth in the coal mining industry, and the safety precautions in some of these older, or reopened mines, isn't always what it should be. If you want to keep your job, in an economically depressed area, you learn not to complain too much. It isn't as if you can just go down the street and get another job.
When the Sago coal mining disaster happened, I mentioned that we would be hearing about more coal mining disasters.