Ontario

The train's cargo was rail ties, so wood treated with coal tar creosote to resist weathering. By my understanding, that type of creosote has a low flash point and if enough vapour had accumulated, it could have been ignited by just about anything. I don't think that normally happens when you're just dealing with treated wood rather than a tanker car of creosote, though, so this might have been a fluke. Or someone might have to reconsider whether wood that's undergone this kind of treatment is "dangerous goods" or not.

What the train crew thought they were doing when they stopped the burning train in a residential area is another question. My guess is that they panicked and weren't thinking straight.