The more photographic evidence I see, the more and more it looks like a heat/flash event occurred at altitude and certainly before wreckage hit the ground.
Whatever the exact cause and sequence of events, this must surely exclude simple mechanical, structural and crew-related actions as the cause because they would simply have not resulted in a fire event.
It would be hasty and unwise to read too much into the suspension of UK airline flights from SSH and an imminent COBRA meeting, but it would not be unreasonable to conclude that those in authority now have information (that we don't have) that gives them a good reason to be cautious.