By Brian Ries, Veronica Rocha, Rob Picheta, Euan McKirdy, Jessie Yeung, Gianluca Mezzofiore and Paul P. Murphy, CNN
From CNN’s Martin Goillandeau and Chris Liakos in London
The total amount of donations by French business leaders and businesses for the reconstruction of Notre Dame confirmed by CNN so far has topped $700 million.
The latest donations of $28 million come from French billionaires Marc Ladreit de Lacharrière, Martin and Olivier Bouygues and the Crédit Agricole — Pays de France Foundation.
In a statement, French bank Crédit Agricole said it was "sharing the collective emotion caused by the damage to this jewel of our heritage."
The bells on Westminster Abbey in London will ring out at 5:43 p.m. local time to mark the moment the Notre Dame fire began, UK Prime Minister Theresa May said.
She said the move would “underline our solidarity with France and her people."
“And later this week, on Maundy Thursday, bells will ring at cathedrals and churches across England,” May said.
May said experts from Historic England will coordinate with their colleagues across the area to make an offer of support once the full extent of the damage has been assessed.
“Notre-Dame is one of the most beautiful buildings in the world — a symbol of France and the French people, and cherished across the globe. The images of destruction we saw last night were truly heart-rending,” she said.
She continued: “When it comes to the task of rebuilding, French craftsmen and women are among the finest in the world. As they prepare to embark on this daunting task, we stand ready to offer any UK experience and expertise that could be helpful in the work that lies ahead to restore this magnificent cathedral.”
Workers will attempt to preserve the infrastructure of the Notre Dame over the next 48 hours, French Interior Minister Christophe Castaner told reporters outside the cathedral.
There is still structural risk to the building, which is being surveyed, he said.
Castaner added that it will take an enormous amount of time to reconstruct the building, saying that the process would take "days (and) months."
He said there was no suggestion that the cause was anything other than accidental, but confirmed that an investigation is underway to identify the precise reason for the blaze.
From CNN’s Saskya Vandoorne in Paris
Some details of the chronology of Monday's fire are beginning to emerge.
At 6:20 p.m. local time (12:20 p.m. ET), security guards at the Notre Dame first heard the fire alarm and evacuated the cathedral, even though they didn't see any sign of a fire, a spokesman for the Paris fire brigade told CNN.
The fire alarm rang again at 6:43 p.m. local time (12:43 p.m. ET). That's when the cathedral’s security officers noticed the fire, Paris Prosecutor Rémy Heitz confirmed during a press conference on Tuesday.
As Paris looks to restore its iconic cathedral to its former glory, it appears funding won't be an issue.
French cosmetics company L'Oréal, along with The Bettencourt Meyers family and the Bettencourt Schueller Foundation, have said they will donate 200 million euros ($226 million) to the restoration efforts.
That puts the amount of donations so far from French tycoons and businesses, confirmed by CNN, at 601 million euros ($679 million).
That total doesn't include money from the city of Paris and the French government.
Paris mayor Anne Hidalgo has tweeted a video of artworks being carefully removed from Notre Dame and taken away for preservation and protection.
Items rescued from the blaze include the Crown of Thorns, which some believe was placed on the head of Jesus during the crucifixion, and the linen Tunic of St Louis.
The works are being sent to Paris City Hall and to the Louvre museum for safekeeping.
From CNN's Eliza Mackintosh
At dawn on Tuesday, as the first blush of sunrise illuminated Notre-Dame de Paris, residents gathered on the left bank of the river Seine to see the damage wrought by a devastating fire that had engulfed the historic cathedral overnight.
"For me, it's much more than stones, it's a part of myself that is burning," said Sarah Virot, 32, who works for a Christian association in the capital.
Notre Dame sits at the French capital's geographical and psychological heart, on a small island called the Île de la Cité, embraced on both sides by the Seine.
It's not just the center of the city, but of the country; from it, all other distances to the capital are measured. And so, for Parisians, the cathedral is not just a religious structure, but a shared legacy.
"I came because I wanted to see something that was hard to imagine," Sarah Parent du Châtelet, 33, told CNN. "I was born in Paris and I know this lady just like an immortal person. It's impossible to imagine Paris without her."
If the Eiffel Tower came to signify the city's sparkling future, Notre Dame has, for generations, embodied its past. "She is the heart of Paris, eternal and spiritual," Parent du Châtelet added.
Read more about how Parisians are coming to terms with a monumental loss here.
News of the devastating fire at Notre Dame will have struck a familiar note to many in York, in northern England.
York Minster, the city's gothic cathedral, was hit by a similar disaster in 1984 when a fire partially destroyed the building.
Both churches can be traced back to a similar time period; Notre Dame was completed in the mid-13th century, while York Minster's West Window and other parts of the site date back to the 14th century.
On Tuesday, York Minster tweeted that the cathedral community had been "shocked and saddened" to see the damage at Notre Dame.
The Archbishop of York, John Sentamu -- the second most senior bishop in the Church of England -- said he had held prayers for Notre Dame on Tuesday morning.
York Minster was painstakingly restored over four years at a cost of just ��2.25 million (about £7 million, or $9 million, in today's money).
In terms of structural damage, Notre Dame may be in better condition, since its vault was primarily made of stone, not wood.
From CNN's Oscar Holland
Those looking for hope amid the devastation of Notre Dame will be heartened by French President Emmanuel Macron's assurance that the French will "rebuild together," and immediate fundraising efforts leading to pledges of 50 million euros ($56 million) and 200 million euros ($226 million) from Paris' City Hall and the luxury goods and fashion house LVMH, respectively.
Assuming the requisite funding is found, how will the process be carried out?
Before distinguishing between the salvageable and the unrecoverable, immediate steps will need to be taken to prevent further damage, architectural historian and broadcaster Jonathan Foyle explains.
"It's already a wet building because of the water that's been pumped on it, so they're going to need to provide some kind of cover from the elements," he told CNN.
"The roof's job was to discharge thousands of tons of water, so where's that going to go? Every time it rains it's going to cause damage at this point, so it's a war of attrition now."
French authorities will ultimately need to take a series of design decisions over how best to rebuild. To do so, they will need to better understand how the medieval cathedral was constructed in the first place.
But the goal of restoration is not always to replicate the past, and modern tastes and technologies may influence how damaged structures are reimagined.
Read more about the task France faces in rebuilding the Notre Dame here.
