On this much, there is general agreement: The destruction of the Lower 9th Ward started with a series of earthshaking explosions. Preliminary evidence shows shoddy engineering, poor maintenance and politics led to the massive failure of the levee system that was supposed to keep New Orleans dry. But long before the evidence was pulled together, another theory had taken root, and it probably won't go away any time soon: that the explosions were caused by dynamite set by someone deliberately blowing up the levees.