Crew quarters is above the main deck. It appears the fire started either in the galley (lithium battery charging station) or in the berthing compartment itself. There are 120V outlets in the berthing compartment, so someone could have been charging batteries down there as well. Toxic smoke, hot as hell lithium battery fire . . . . if you see the video of LASFD putting water on the blaze, you can see the heart of the fire reacting unusually to the water from the hoses. Throw some water on a burning lithium battery and see what happens.
One of the least commonly known problems with lithium batteries (LIPO) is that OEM batteries have a circuit board in every pack that monitors each cell voltage during charge or discharge to make sure the cells stay in their nominal voltage range.
If a cell becomes out of balance with other cells in the pack during charge, for example, the circuit will stop charging that cell.
The difference is between a $50 battery pack and a $30 pack? The $30 pack (cheap chicom knock-off) doesn't have the safety circuit.
When you read stories about people whose cell phones, computers, etc. catch fire, it's because these people replaced the OEM pack with a cheap chicom knock-off.
This incident certainly has all the earmarks of a LIPO fire.
Best explanation so far, from an old sixpac skipper.