Even though the "experts" are still not allowed to enter the building because it's not considered to be stable, the "experts" have now concluded that the fire was caused by a short circuit.
I find that incredibly difficult to comprehend. I don't know what kind of electrical stuff they had in the attic space above the stone vaults and below the roof, but I doubt it would be anything that would cause a fire in the event of a short circuit. They apparently had a fire alarm/detection system. Those operate on low voltage -- 12 or 24 volts. And, unless it was a system as old as the building itself, a fire/smoke detection system would have self-monitoring, so if a short circuit occurred, the system would have initiated a trouble alert.
France, like all of Europe, uses 220-volt electric for lighting and convenience power. 220 volts can make a decent spark, or generate some heat if it shorts. But what was in the attic that could burn? Those roof timbers were so big that they say there are no trees anywhere in Europe large enough to replace them. It takes a LOT of heat to start a timber that big to burning. Thank about your fireplace, or a campfire. Take a log six inches in diameter at 40 or 50 degrees ambient temperature, with the bark scraped off it, and try to light it using a match. Or a Zippo. Not going to happen.
One article speculated that the fire started as a result of a malfunction in an elevator. Since the point of origin was near the intersection of the transept and the nave, there are no elevators there serving the building. There was an elevator of some kind in the scaffolding, for access to the spire they were restoring. That was outdoors, above the (metal) roof, and the scaffolding was steel (except for the plank walkways, I assume). I don't see how a short in the elevator could have started a fire in the attic.
At this point, there isn't enough information to determine how the fire started. IMHO there certainly isn't enough information to label it an act of terrorism ... but there also certainly isn't enough information to determine that it WASN'T an act of terrorism.
