In both of the cases reviewed, the explosives expert could not identify any evidence of the use of conventional explosive devices. Thus, no primary fragments were identified in the debris; no craters or shatter effects were found; and surviving walls, stone bricks, and ceilings were not pitted. Also, investigations revealed that explosion could not have been caused by domestic propane gas. Rather, in each case, there was direct evidence of the use of gasoline as an accelerant in an arson fire that led to explosion. Apparently, as a result of overpressure formed inside the structure during an accelerated fire, venting occurs by lateral movement of the wall bricks in the upper courses closest to the ceiling. This may lead to loss of support of the ceiling slab, which then falls under gravity, causing further collapse of surviving walls. Although the destruction of the structure occurs with explosive violence, the forensic evidence from the scene of the crime usually allows a differentiation of this type of explosion from one caused by domestic gas or a bomb. It is more difficult to distinguish between an accidental and deliberately caused explosion when domestic gas is the fuel. 5 figures and 6 references