they probably used C4 to exploded it.
I was out in Fallon, NV at a Naval base for 4 months rebuilding Targets in the middle of the dessert for their Top Gun School.
Any time we came across any kind of metal sticking out of the ground we had to call EOD to exploded it. It used to be a test site for live bombs, sometimes they wouldn't go off so they would just blow everthing up that they came across, just incase it was still live.
Now they use fake bombs for target practice, when it lands it lets off a puff of powder so that the pilot can tell if he hit the target or not.