Since everyone' still speculating, I'll add my own. Maybe it is indeed a water heater or something similar. If the pressure relief valve isn't inspected periodically, it can jam and force pressure to build inside the water heater until it explodes. This is an example of damage even a 5-gallon water heater can cause: http://www.masterplumbers.com/plumbn...1/dec/avon.asp Water heaters in a mall are much much bigger.
Last edited by Jun aka Pekto; January 28th, 2008 at 06:09 AM.