Why was I-49 in Upper Lafayette on Fire Today? [VIDEO]

I was driving on I-49 in Upper Lafayette this afternoon and I saw that the area was very smokey.

I turned onto the service road to get a better view and was able to grab a few pictures.

The grass along the side of I-49 was burning in at least 3 places, each just over 500 feet apart (guesstimation only).

I don't know what caused the fire(s) alongside the interstate to ignite, but firefighters were out there with a hose and straight-handled swatter, doing their thing (see the video lower in the story).

I would blame the fire on discarded cigarettes, but what are the odds of having 3 discarded cigarettes within a quarter-mile of each other? If it wasn't a cigarette, what was it?

The thought of a vehicle idling alongside the interstate came to mind, but the location of the burning grass doesn't lend credence to that hypothesis: the embankment was too steep for a vehicle to park, and part of it was behind a railing.

I'm grateful for the fire department and recognize the risks they take to keep us safe.

So, what gives? What could have started those fires on the side of I-49?