FDR and CVR requirements.
TSO C123a (CVR) and C124a (DFDR)
Fire (High Intensity) 1100°C flame covering 100% of recorder for 30 minutes. (60 minutes if ED56 test protocol is used)
Fire (Low Intensity) 260°C Oven test for 10 hours
Impact Shock 3,400 Gs for 6.5 ms
Static Crush 5,000 pounds for 5 minutes on each axis
Fluid Immersion Immersion in aircraft fluids (fuel, oil etc.) for 24 hours
Water Immersion Immersion in sea water for 30 days
Penetration Resistance 500 lb. Dropped from 10 ft. with a ¼-inch-diameter contact point
Hydrostatic Pressure Pressure equivalent to depth of 20,000 ft.
Here are the parameters required to be recorded:
I'd rather wait for the professionals to determine the cause.
By the way, the results of the investigation are all based on probabilities. This is the most likely event etc. It is not necessarily definitive. In cases especially like this the actual cause may never be known.