Update 13h30GMT: The l'Oréal cosmetics group and the Bettancourt family have donated €200million for Notre-Dame's restoration effort. This now brings the total already pledged, within 24hours of the cathedral's destruction, to €600million.
This comes as President Emmanuel Macron has vowed that the monument will be rebuilt after its spire and roof collapsed Monday night in a blaze thought to be linked to extensive renovation work.
French billionaire Bernard Arnault announced Tuesday that he and the LVMH luxury conglomerate he controls would give €200 million for the reconstruction efforts.
The pledge came after Arnault's rival Kering, the fashion group founded by fellow billionaire Francois Pinault, offered 100 million euros to help "completely rebuild Notre-Dame".
French oil company Total also pledged €100million to help with the reconstruction.
Paris Mayor Anne Hidalgo also said Tuesday that the city would unlock 50 million euros, and has proposed holding an international donors' conference in the coming weeks to coordinate the pledges to restore the gothic architectural masterpiece.
The Ile-de-France region comprising the greater Paris region is to provide another 10 million euros.
Rare materials and expertise required
Meanwhile, specialised craftsmen and rare materials will be needed to restore the monument, which welcomes more than 13 million visitors each year -- an average of more than 35,000 people a day.
The head of a French lumber company told FranceInfo radio that it was ready to offer the best oak beams available to rebuild the intricate lattice that supported the now-destroyed roof, known as the "Forest".
According to Sylvain Charlois of the Charlois group in Murlin, central France, "the work will surely take years, decades even, but it will require thousands of cubic metres of wood. We'll have to find the best specimens, with large diameters."
UNESCO pledges support
The United Nations' Paris-based cultural agency UNESCO has also promised to stand "at France's side" to restore the site, which it declared a world heritage site in 1991.
UNESCO's secretary general Audrey Azoulay said in a statement earlier Tuesday that "we are already in contact with experts and ready to dispatch an urgent mission to evaluate the damage, save what can be saved and start elaborating measures for the short- and medium-term".
Rebuilt in years?
The renovation work is likely to cost hundreds of millions of euros over several years, if not decades, though experts breathed sighs of relief that the damage was not worse.
However many officials are urging the government to mobilise the resources to quickly restore the cathedral.
Speaking outside the cathedral today, former culture minister Jack Lang said "since yesterday I've been hearing that it will take a decade, what nonsense!".
Barak Obama on fire in Notre-Dame
Notre Dame is one of the world’s great treasures, and we’re thinking of the people of France in your time of grief. It’s in our nature to mourn when we see history lost – but it’s also in our nature to rebuild for tomorrow, as strong as we can. pic.twitter.com/SpMEvv1BzBBarack Obama (@BarackObama) April 15, 2019
Instead he has called for an ambitious three-year project to rebuild the destroyed roof and its towering spire, which collapsed as a burning ember around two hours after the blaze erupted.
Lang added: "Y..ou have to set a short deadline, as we've done in the past with other exceptional works."
The gothic structure had already been undergoing an €11million-euro overhaul financed by the French state to repair damage inflicted by time, pollution and the weather.