French president Emmanuel Macron has vowed to see Notre Dame rebuilt within five years as more than €600 million (£520m) was pledged to help restore the cathedral to its former glory.
The inferno that raged through the building for more than 12 hours destroyed its spire and its roof, but spared its twin medieval bell towers.
A frantic rescue effort saved the monument’s “most precious treasures”, including the Crown of Thorns purportedly worn by Jesus.
Also surviving was the Roman Catholic cathedral’s famous 18th-century organ that boasts more than 8,000 pipes after a plan to safeguard the masterpieces and relics was quickly put into action after the fire broke out on Monday. Statues removed from the roof for restoration just days ago also were saved.
But the cathedral’s high altar was damaged by falling debris when the spire collapsed.
Authorities consider the fire an accident, possibly as a result of restoration work at the global architectural treasure that survived almost 900 years of tumultuous French history, but was devastated in the blaze on the second day of Holy Week.
Paris prosecutor Remy Heitz said the inquiry into what caused the fire would be “long and complex”.
Fifty investigators were working on it and would interview workers from five companies hired for the renovations to the cathedral’s roof where the flames first broke out.
Mr Macron promised in a televised address to the nation that “we will rebuild Notre Dame cathedral even more beautiful”.
He said that “we can do it and once again, we will mobilise” to do so.
The president, who said “we have so much to rebuild”, thanked firefighters and police, as well as donors who are giving money for the renovation. Millions of euro have also been pledged from French families and companies, including Total and L’Oreal Group.
The president of the University of Notre Dame said the school would give $100,000 (£76,621) towards Notre Dame’s renovation.
Just under 400 firefighters worked through the night to control the inferno. Two police officers and one firefighter were injured.
Tourists gathered outside Westminster Abbey yesterday at 5:43pm – 24 hours after the fire started – after Prime Minister Theresa May said the bells would toll with others across the country tomorrow in solidarity.
Mrs May described the images of destruction as “truly heart-rending”. The tragedy has prompted an outpouring of support internationally, with the Queen saying she was “deeply saddened” and Pope Francis phoning Mr Macron to express his solidarity.
French culture minister Franck Riester said some of the most valuable treasures were stored overnight in the Paris town hall and would be moved to the Louvre museum “as soon as possible”.
He said major paintings were not likely to be removed until Friday morning, adding: “They have not been damaged, but there could be some damage from the smoke so we are going to take them safely and place them in the Louvre.”
The fire, which broke out as the last crowds of tourists ended visits just before 6pm BST (7pm local time), was finally declared to be “fully extinguished” yesterday morning.