[Blue Jays]

President 0bama quickly announced, "It is NOT terrorism!" approximately .000485 seconds after the last explosion was heard, during which time he apparently completed an exhaustive investigation on his own.

[Eleutheria5]

So it must be terrorism.

[Robert A Cook PE]

A non-terrorist explosion at a coal-fired plant is possible: Most likely is a coal dust explosion within (or above) the coal pulverizers that receive finely crushed coal from the feed hoppers, then blow that coal-and-air powder mix up into the burners. They are notoriously dirty, and even grain elevators can blow up if the wrong powder-air mix ratios are created.

Hydrogen surrounds and cools the generators - that can leak and be set up. Other water treatment and control chemicals are not likely to explode, but they are volatile and some are deadly themselves like ammonia.

Too little info in this story.