But it was as you report the owner was opening the case of the tablet. They punctured the battery and it didn't explode but did smoke and swell.
I have a Acer One Tablet. It was purchased less then a year ago. The battery exploded. Opening the tablets case it was not plugged in at the time. I phoned Acer and they will not replace it and seam to care about it exploding. I would not buy Acer products again nor would I trust Acer products around Children.