I must admit that the idea of those hundreds of years old beams, taking fire all of the sudden, just like that, still puzzles me.
NOTRE DAME - AL AQSA en feu - SORAL - A T ON LE DROIT D'ETRE CON
I checked pictures of scaffolding before the fire - they do not extend to the ground.
It means that nobody who was unauthorized to be there was there.
Either fire was an accident or one should look for arsonist(s) among construction crew.