I'll bet my last penny that it isn't an unvented cylinder.
I know unvented cylinders can go bang, but:
a: They tend to go off like a rocket, with the bottom welded seam as a weak spot. They tend to go up and not as much out.
b: They have simple factory fitted safety components (the combined temp/pressure relief valve) which would fail safe - only a complete fool would take this out and cap it.
c: They don't smell like gas.
d: They generally don't totally destroy houses and make the neighbours feel like an earth quake just occurred.
Gas is the most legislated trades of all and with good reason.
With electrics if you get a dangerous fault, you'll generally kill one victim.
With water, the flood damage can run into thousands but you'll generally not kill anyone (though it does happen).
With other trades carpentry, plastering, tiling, you can have dangerous work completed but its more rare and again more likely to harm a single victim.
With gas, especially explosions. You tend to wreck whole buildings and often neighboring buildings have to be pulled down too. When people die, it's often in numbers.
The explosion of a bulk LPG tank a few years ago killed over 20 people. The gas leak dropped into the drainage, under the building and BOOM. Totally destroyed a whole factory and killed most of the people inside.
If anyone touched that gas supply (registered or not) in the last 12 months, I'll imagine they'll be going inside.
A child has died it's a tragedy. Very sad.
