Is it near Alcoa Highway exit off 40 near downtown? I went through there yesterday and could hardly see 5 ft in front of me.
Sadly, the fire doesn't have enough steam to make it downtown and torch the worthless Convention Center to the ground.
Ya, the mulch likely combusted. Happens all the time in the South. It generates a lot of heat and if the top layers dry out, "poof." You'll see signs in mulch beds at banks warning you not to toss a cigarette. I've also seen mulch spontaneously combust right in front of my eyes at UT once, while looking out a window during a meeting. Heated wood gives off wood gas, which is the same as gasoline vapor.
i drove by it yesterday. shit is crazy. hopefully the rain helped. there's also a twitter handle for it.