Continuity between B+ and OUT... flames

[Everest]

I am not sure if this is the correct forum for this, apologies if I've posted it in the wrong place.  The device is a DNA200

I was sitting at my desk today, and suddenly my RDA erupted into flames.  I yanked the side cover off my enclosure and pulled out the battery (a 3S 1300mAh lipo pack) and found it to be cool - I still chucked it out on the porch to be safe.  Disassembling the device, no components seem to have fried, the fuse is intact.  Checked function of the 'fire' button and it is correctly open/closed like a switch should.  Then I checked continuity between the battery connector and the 510 connector - low and behold there is no resistance between negative battery / negative 510 and positive battery / positive 510.  I de-soldered all the connections (board to 510, battery connectors) to check the naked board - and sure enough there is continuity between the battery +/- straight through the device to the output pads.  

 

Any ideas regarding what component might have failed?  So strange that it was literally just sitting on the desk, hadn't taken a puff in ~10 minutes, and it just went off.