Cindy, there have been quite a few explosions in San Diego of late, correct?
Sun May 4, 2008
FBI looks into San Diego courthouse explosion
The FBI recovered more than 100 nails and shrapnel as far as two blocks from the courthouse, Foxworth said. Investigators believe the bomb may be linked to a blast April 25 that shattered the glass door of a FedEx building in San Diego
Could be a simple matter of not fully closing valves on gas welder tank etc..