From KBDiverServices:

There were a series of AL tanks produced by a couple of manufacturers prior to 1989 that have proven more likely to explode than others due to the material they were made with. These AL tanks are the only tanks that require the Visual Plus test. Many shops will not fill them at all - even if they pass the visual plus test.

As far as o2 being the cause, o2 in the cylinder would expand in volume the same as air and cause a burst disc to rupture before the tank would explode. Certainly o2 is a more volatile gas when it comes to producing flame. It is why tanks and valves must be o2 cleaned before filling with 100% o2 and/or before partial pressure nitrox fills - which require 100% o2 be put into the cylinder before air.

Again, a tank being filled with 100% o2 is more likely to ignite, start a fire and potentially explode during filling - especially if the valve and/or tank have contaminants in them or in new tanks where the smallest sliver of steel remains lodged in the valve or interior of the tank.

It is no more likely in my opinion that a tank being carried - filled with o2 - simply exploded than a tank with air - unless that tank was overpressurized, left in sunlight or heat all day and the burst disc was changed out. The same scenario in which I could see a tank filled with air exploding. In both cases, it would be a much more likely an event if the AL tank was produced prior to 1989.