Macron wants Notre Dame to rise from the ashes

France vowed to rebuild the iconic, fire-ravaged Notre Dame cathedral "even more beautifully", and to complete the work within five years, as donations supporting the work flooded in from all over the world.

French President Emmanuel Macron said the 850-year-old Gothic building will battle back from Monday's fire, which destroyed much of the roof and that caused the steeple to come crashing down.

"We'll rebuild Notre Dame even more beautifully and I want it to be completed in five years," Macron said in a televised address on Tuesday evening. "We can do it …It's up to us to convert this disaster into an opportunity to come together."

He said the building work should be completed by the time Paris hosts the Summer Olympics in 2024.

"The fire at Notre Dame reminds us that our history never stops and we will always have challenges to overcome," he added.

But Macron's optimism was out of step with some experts, who said the rebuilding could end up taking much longer.

Eric Fischer, who led a recent restoration of the1,000-year-old Strasbourg cathedral, told AFP news service Notre Dame's rebuilding may last decades. And Frederic Letoffe, who heads a group of companies involved in the restoration of historic monuments, told the BBC he believes it will take 10 to 15 years. He said much needs to be done to make the site safe before restoration can begin following the 15-hour battle to extinguish the fire.

Audrey Azoulay, director-general of the United Nations' cultural organization Unesco, which designated the cathedral a World Heritage site, told the Guardian newspaper restoring Notre Dame "will last a long time and cost a lot of money".

Remy Heitz, meanwhile, the public prosecutor in Paris, said 50 people are probing the cause of the fire. So far, there is no suggestion arson was to blame and investigators are working on the theory it was an accident.

Heitz said the probe is likely to be "long and complex".

Investigators started by talking to workers from five companies involved in extensive pre-fire renovations at the cathedral.

But there was some good news on Wednesday when it transpired the extent of the damage could have been far worse.

Deputy Interior Minister Laurent Nunez told reporters 400 firefighters saved the cathedral's main structure and its two bell towers during a frantic 15-to-30 minute window that, if things had not gone well, could have ended in the total destruction of the site.

Macron also heaped praise on firefighters, saying they took "extreme risks"while saving the bulk of the building.

Firefighters reportedly put their lives on the line by staying inside the burning building and creating a wall of water that protected the two towers on the west facade.

Nunez said experts have, so far, not been able to access much of the site because of the continued danger, but noted that firefighters had used drones to survey the building. Initial sweeps appear to show that at least one of the famed rose windows survived the inferno while other stained-glass windows were lost. The flames appear to have missed an 18th century organ, but it is not yet known whether the instrument was damaged in other ways.

Culture Minister Franck Riester said artwork and religious items saved from the burning building, which included a crown of thorns that was said to have been worn by Jesus before his crucifixion, will be housed in the Louvre museum while the cathedral is restored.

So far, the private sector has pledged more than 700 million pounds ($900 million) toward rebuilding and restoring the cathedral.

Duncan Wilson, chief executive of the conservation organization Historic England, told the Guardian: "Structural engineers, stained-glass experts, stone experts, are all going to be packing their bags and heading for Paris in the next few weeks."