It seems to be taking a very long time to find out the root cause of this fire. Six days seems to be unusually long and
Fire/incendiary investigations often can be the toughest to crack specially if one looks for a 'root cause'. Six days is absolutely nothing. I would argue that a 'root cause' of TWA800 fire/explosion was never found - only the best theory was adopted after years of futile attempts trying to reproduce events. Did they ever find root cause of the 787 batteries fires/failures - NO. I wouldn't be surprised if the preliminary report in this case will offer temporary recommendations and investigation will continue.