Its iconic twin bell towers remained visibly intact. Paris officials said the world-famous 18th-century organ that boasts 8,000 pipes also appeared to have survived, along with other treasures inside the cathedral, after a plan to safeguard heritage was quickly put into action.
Paris Deputy Mayor Emmanuel Gregoire described authorities' "enormous relief" at the salvaging of pieces such as the purported Crown of Christ, which were transported to a "secret location" after the fire. Statues removed just days ago for restoration work were also spared.
At dawn, the twin 69-meter towers swarmed with building specialists and architects.
"The entire fire is out," declared Paris firefighters' spokesman Gabriel Plus, adding that workers were "surveying the movement of structures and extinguishing smoldering residues."
"The task is — now the risk of fire has been put aside — about the building, how the structure will resist," said Junior Interior Minister Laurent Nunez in front of the cathedral.
One of the city's five senior vicars, Philippe Marsset, told AP: "If God intervened (in the blaze) it was in the courage of the firefighters."
"Notre Dame was destroyed but the soul of France was not," Michel Aupetit, archbishop of Paris said on RMC radio. Officials consider the fire an accident, possibly as a result of the restoration work at the global architectural treasure.
Paris prosecutor Remy Heitz said the investigation would be "long and complex." Fifty investigators were working on the probe, he said and would be interviewing workers from five companies hired to work on renovations to the cathedral's roof, where the flames first broke out.
Heitz said an initial fire alert was sounded at 6:20 p.m. Monday but no fire was found. The second alert was sounded at 6:43 p.m. and a blaze was discovered in the roofing at that point.
News that the fire was probably accidental has done nothing to ease the national mourning.
"Notre Dame has survived the revolutionary history of France, and this happened during building works," said influential former Culture Minister Jack Lang.
French President Emmanuel Macron pledged to rebuild the cathedral that he called "a part of us" and appealed for help to do so.
As France woke up in collective sadness, its richest businessman, Bernard Arnault, and his luxury goods group LVMH pledged 200 million euros ($226 million) for the reconstruction.
A communique said the Arnault family was "in solidarity with this national tragedy, and join in the reconstruction of this extraordinary cathedral, a symbol of France, of its heritage and togetherness."