WAF:

You are indeed correct. I thought about that, too, as I looked at the overhead video. Apparently there was a train passing through approximately 15 minutes before the fire was reported or seen, if the news reports are accurate. The circumstances that form my opinion (and that's all it is) that something else happened are the facts that during the early development of the fire, as seen from overhead, no part of the track surface was burning... and all the fire involvement was UNDER the structure. One would not expect this if a stray spark ignited a pool of some flammable material on the tracks.

All is speculation, of course, until the investigation is concluded. I think it's healthy to share unofficial ideas, theories and opinions based on observations, experience and knowledge. (Interesting that someone else on this thread thinks this is "flaming" him.)