Miracle Gro - You could start a fire!

I sent this email last week. I have had no response.

Good day.
This very well may be the first such email you have ever received; I'm sure the situation is rather rare. What I would prefer to avoid is a static, autonomic response saying "Mr. Shambles...our studies indicate...if we can further not assist you...." You know. That kind of thing.

Here's the situation: For a year and a half, 3 medium-sized (gallon?) pots, filled with a mix of Miracle Gro Potting Mix and some organic, generic soil was used to grow flowers. It was always outside and once a week or so, we'd hit it with Miracle Gro Garden Feeder while watering our garden.

We moved. To an apartment. Being on the first floor, we set the pots outside so the flowers could be part of the door decoration. Already struggling from the move, the plants soon died and we began using the pots as ashtrays. This was six months ago.

The pots have remained dry, in the external hallway of an apartment complex, for the last six months. Yesterday afternoon, we came home to something smelling distinctly of burning. Because of the strong local wind, it wasn't until late in the evening that we identified the burning as coming from our ashtray soil pots. Well, the one we were using as an ashtray.

I put my hand over the pot. It was hot. Really hot. When the wind paused, smoke plumes rose from our previously-Eden-esque pot of wonder. Really, it was a new pot of wonder, growing fire instead of life. Obviously, once realizing the source of the fire smell, of the smoke, we dumped water into the pot. It sizzled like dumping a gallon of water on a barbecue.

The stats: Normal potting soil could not have done this, so it's either the mix of chemicals in the soil, cigarette heat, and wind, or it's a miracle of Christ. Since I don't necessarily believe in the latter in the presence of fertilizer (which can be used to make bombs), I'm just curious.

So the questions: Have you ever heard of a pot, kept dry for some time, turning into a furnace? None of the embers were visible, but the heat and the smoking, have you ever run into this? Is there something we can avoid in the future to avoid a situation where our smoldering grill-pot, sitting right next to our vinyl siding, might be kept safe?

Honestly, I'm just glad I caught it. I know it's probably a confluence of circumstance, but your product set soil a-smoldering. I just worry that it's something that might happen again.

I'll be happily awaiting your answers.

Thanks for your time,

What the hell? A flower pot turns into a furnace. It's reminiscent of the underground burning of the real-life Silent Hill Pennsylvania town. And until now I couldn't imagine how something like that could happen.

Updates hopefully...