2012 Macbook Air Fire

My family and I had a surprise wake up this morning around 3:30 when our smoke alarms started going off. My dad ran into the living room and found that my Mom's Apple Refurbished 2012 Macbook Air, which had been put to sleep, had (seemingly) spontaneously combusted - lighting the ottoman and surrounding carpet on fire. Fortunately, he was able to put out the fire quickly with fairly minimal damage to the furniture and the floor.

After waiting for everything to cool off, I inspected the computer. It was covered it ash, charred plastic and melted fabric. Surprisingly, it immediately turned back on when I opened it up. It was fully responsive. I logged in, fired up safari - everything was working (and operating at a normal temperature).

My mom has never had any issue with the computer getting hot. It was laying on a cloth ottoman (pictured below), but it was laying flat. None of the ports were obstructed.

I've attached some photos of the computer and the damage. Would anybody be able to shed some light on what in the world happened? We've already called the insurance company and I plan on calling Apple tomorrow morning.