Authorities in the French capital say there’s no reason to suspect criminal activity caused the fire that gutted the centuries-old cathedral in April. But they still haven’t pinned down exactly what did, speculating that either faulty electrical wiring or a poorly stubbed-out cigarette was to blame. According to chief prosecutor Remy Heitz, those conclusions were based on interviews with around 100 witnesses — though he added that “deeper investigations, using significant expertise” lie ahead.
How will investigators proceed? They’ll continue combing through debris for traces of electrical circuits, as well as reviewing witness testimony for a full inventory of flammable materials that had been stored in the cathedral.