The cause of the fire may have been a short circuit that reached a reservoirstore of paraffin, a solid fuel used in the manufacture of candles. The cause of the fire may have been a short circuit that reached a store of paraffin, a solid fuel used in the manufacture of candles.

Everything's really good. Just a bit of a nitpick, but I've just never encountered 'reservoir' being used with solid things, only liquids or 'fluid' things. Here's what I mean: -a place where fluid collects, especially in rock strata or in the body. "big oil reservoirs are becoming harder to find" -a receptacle or part of a machine designed to hold fluid. "if all three colours overlap then a black dot is printed from the black ink reservoir" These are two of the defininitions of reservoir. I think store does a better job in this sentence.