Smoking on the escalators, wooden steps, and build-up of trash in the inaccessible area underneath them all contributed.
It might look long but is still really interesting to read, the simple questions that needed to be answered, the interviews and the conclusion.
https://en.wikipedia.org/wiki/Trench_effect
My normal commute would have taken me right into the center of the fire.
Smoking on the escalators, wooden steps, and build-up of trash in the inaccessible area underneath them all contributed.