The fire broke out 5-10 minutes after the place closed to tourists.
Very easy for a “tourist” to stay behind in a hiding place, having spotted some fuel sources, esp. related to the wood renovation.
That’s my working guess. It’s also my guess that the French PTB will suppress any link to Islam.
As old as the wood is...it’s my guess it was covered in pitch as a preservative. Very flammable. Just makes me sick! Such a beautiful place and first placd I visited.