The fire that almost burned down Redding California a few years back was caused by safety chains from a guy pulling a trailer. The chains dragging on the ground caused a spark which ignited the brush on the side of the road. The problem was it was on government land. So instead of putting the fire out immediately. They had a meeting to decide whether it started naturally and therefore should they let it burn. By the time they decided to put it out, it was out of control.
Yes, that is often how farm field fires get started.