Static electricity might have ignited a leak on a liquid fuel cell. Depending on how they're configuring their guidance systems, their OWN radar could have initiated a launch/auxilliary fuel ignition sequence. Dropping a warhead is generally not a problem (scary, but not really an issue: the warhead is ironically the safest part of most missiles). Dropping an entire missile, with the result of leaked fuel? That is another matter. So for those saying "The Mossad did it!" umm, you sound really stupid.
Magnitude 6.1 quake hits Panama-Colombia border (Reuters)