There’s the engine of some sort of vehicle humming to the northeast. It moves with me, and produces smoke. Reloading works for a time, but it eventually comes back. I have no explanation for this.
I have also noticed an empty space emitting smoke, that seemed to move with me, staying on the same position on the screen at all times. I was running from a horde of zombies at the time and died shortly after, so I didn’t get much of a look at it, but it’s likely the same thing.
Sounds like it to me.