PARIS — Fueled by a lattice of centuries-old timbers, the fire moved hungrily across Notre Dame’s rooftop toward the cathedral’s iconic spire. It belched yellow smoke, spitting out gritty particles of wood, stone, lead and iron and wanted more. Far below, their vision obscured by fumes and tears, firefighters, priests and municipal workers passed treasures hand-to-hand, hoping the speed of desperation could outrun the flames.

They had 66 minutes.

The first alarm sounded at 6:20 p.m., silencing the priest and a few hundred worshippers and tourists inside.

“Everyone was immobilized by shock for maybe a minute,” said Johann Vexo, who was in the organ loft for Monday Mass. Shock, but no panic. The rear doors opened and within a few minutes, the cathedral was empty, he told Ouest-France newspaper.

For 23 minutes, it seemed like a false alarm. Then at 6:43 p.m. a second smoke detector went off and the fire showed its face, flickering in the wooden timbers and visible to anyone looking north from Paris’ Left Bank.

The first firetrucks lumbered through rush-hour traffic, blasting their two-tone sirens at full volume to reach the island that is the historic and geographic heart of Paris. For that first half-hour, it looked like the fire couldn’t possibly leave more than a small age mark on the nearly 900-year-old building — more akin to the inevitable wear on stone’s rough edges than the fury of the French Revolution that left it in ruins for decades.

Across the Seine in City Hall, Mayor Anne Hidalgo glanced out the window during an evening meeting to see a yellow cloud blotting out the sky. She rushed to the island.

“I came here and felt powerless as the flames overtook the cathedral,” she said Tuesday.

Bridge after bridge along the Seine filled with somber onlookers, all facing the cathedral built for the ages. They dotted the stone walkways that line the river. They wept as flames overtook the rooftop spire.

Below it, nestled deep in the cathedral, was the treasure chest, keeper of Notre Dame’s most sacred relics.

Firefighters cracked the chest open, pulling out the Crown of Thorns revered as the one worn by Jesus Christ at his crucifixion. Made of rushes wrapped into a wreath and tied with gold filament, it had been kept under glass since 1896. The tunic of St. Louis, believed to have belonged to King Louis IX, came out of the chest along with fragments of the cross and a nail, said Patrick Chauvet, rector of Notre Dame Cathedral.

The relics were safe.

Then came the artwork.

“We had to get them, in the smoke, as debris was falling to protect them,” Gen. Jean-Claude Gallet of the fire brigade told BFM television.

At 7:49 p.m., the 19th-century spire that was the architectural masterpiece of Eugène Emmanuel Viollet-le-Duc and his post-Revolutionary restoration broke apart and fell through the nave. The bronze weathercock tumbled, taking with it three relics sealed inside in 1935.

It had been 66 minutes since the first flames were spotted.

The sky above the cathedral flamed orange, and the fire lurched toward Notre Dame’s iconic towers, then slipped inside.

As darkness fell, 20 firefighters climbed inside the two towers “at great risk to their lives, to attack the fire from the inside and save the building,” said Laurent Nunez, deputy interior minister.

The spire was lost. Could Notre Dame itself be saved? From inside and out, firefighters fought the battle of their lives — a battle for the ages.

At 9:49 p.m. Nunez voiced the fear that haunted Paris and beyond. The smell of smoke had long since reached beyond the city center, permeating homes and apartments miles (kilometers) away. Sirens wailed ceaselessly. Hundreds of firefighters were doing their utmost. And, Nunez said, no one knew whether it would be enough.

The 20 firefighters struggled on in the towers. Red-hot embers floated down from the glowing hole where the spire once stood, settling on the blackened marble floor and the pile of debris that was all that was left of the spire. It had been “a masterwork of Viollet-le-Duc” and a tribute to what restoration could achieve, said Kevin Murphy, an expert on historical restoration from Vanderbilt University. It was gone, as were the roof’s irreplaceable ancient wooden beams, cut from trees that were alive a millennium ago.

At 11:23 p.m., the fire chief said the rest of the structure, including the cathedral’s twin bell towers, had been saved. It had been within 30 minutes of collapse.

It took 10 more hours for the last flames to be put out. The spire’s bronze rooster, long a symbol of France, was found Tuesday, deformed by the heat but recognizable nonetheless.

“Beyond emotion, beyond words, beyond tears,” Christophe Castaner, France’s interior minister, said Tuesday as he visited the cathedral, “What I want to express is the pride of the men and women who committed to saving Notre Dame.”

Story: Lori Hinnant

LONDON — Notre Dame in Paris is not the first great cathedral to suffer a devastating fire, and it probably won’t be the last.

In a sense, that is good news. A global army of experts and craftspeople can be called on for the long, complex process of restoring the gutted landmark.

The work will face substantial challenges — starting immediately, with the urgent need to protect the inside of the 850-year-old cathedral from the elements, after its timber-beamed roof was consumed by flames .

The first priority is to put up a temporary metal or plastic roof to stop rain from getting in. Then, engineers and architects will begin to assess the damage.

Fortunately, Notre Dame is a thoroughly documented building. Over the years, historians and archeologists have made exhaustive plans and images, including minutely detailed, 3-D laser-scanned re-creations of the interior.

Duncan Wilson, chief executive of the conservation organization Historic England, said Tuesday that the cathedral will need to be made secure without disturbing the debris scattered inside, which may provide valuable information — and material — for restorers.

“The second challenge is actually salvaging the material,” he said. “Some of that material may be reusable, and that’s a painstaking exercise. It’s like an archaeological excavation.”

Despite fears at the height of the inferno that the whole cathedral would be lost, the structure appears intact. Its two rectangular towers still jut into the Paris skyline, and the great stone vault stands atop heavy walls supported by massive flying buttresses. An edifice built to last an eternity withstood its greatest test.

Tom Nickson, a senior lecturer in medieval art and architecture at London’s Courtauld Institute, said the stone vault “acted as a kind of fire door between the highly flammable roof and the highly flammable interior” — just as the cathedral’s medieval builders intended.

Now, careful checks will be needed to determine whether the stones of the vaulted ceiling have been weakened and cracked by the heat. If so, the whole vault may need to be torn down and re-erected.

The cathedral’s exquisite stained-glass rose windows appear intact but are probably suffering “thermal shock” from intense heat followed by cold water, said Jenny Alexander, an expert on medieval art and architecture at the University of Warwick. That means the glass, set in lead, could have sagged or been weakened and will need minute examination.

Once the building has been stabilized and the damage assessed, restoration work can begin. It’s likely to be an international effort.

“Structural engineers, stained-glass experts, stone experts are all going to be packing their bags and heading for Paris in the next few weeks,” Alexander said.

One big decision will be whether to preserve the cathedral just as it was before the fire, or to take a more creative approach.

It’s not always a straightforward choice. Notre Dame’s spire, destroyed in Monday’s blaze, was added to the Gothic cathedral during 19th-century renovations. Should it be rebuilt as it was, or replaced with a new design for the 21st century?

Financial and political considerations, as well as aesthetic ones, are likely to play a part in the decision.

Getting materials may also be a challenge. The cathedral roof was made from oak beams cut from centuries-old trees. Even in the 13th century, they were hard to come by. Nickson said there is probably no country in Europe with big enough trees today.

Alternatives could include a different type of structure made from smaller beams, or even a metal roof — though that would be unpopular with purists.

The restored building will have to reflect modern-day health and safety standards. But Eric Salmon, a former site manager at the Paris cathedral, said it is impossible to eliminate all risk.

“It is like a street accident. It can happen anywhere, anytime,” said Salmon, who now serves as technical director at the Notre Dame cathedral in Strasbourg, France.

The roof of Strasbourg’s Notre Dame was set ablaze during the 1870 Franco-Prussian War. It took up to five years to restore the wooden structure. Nowadays the roof is split into three fire-resistant sections to make sure one blaze can’t destroy it all. Smoke detectors are at regular intervals.

Still, Salmon said that what worked in Strasbourg may not be suitable for Paris. Each cathedral is unique.

“We are not going to modify an historic monument to respect the rules. The rules have to be adapted to the building,” he said.

Experts agree the project will take years, if not decades. Audrey Azoulay, director-general of UNESCO, the United Nations’ cultural organization, said restoring Notre Dame “will last a long time and cost a lot of money.” A government appeal for funds has already raised hundreds of millions of euros (dollars) from French businesses.

But few doubt that Notre Dame will rise again.

“Cathedrals are stone phoenixes — reminders that out of adversity we may be reborn,” said Emma Wells, a buildings archaeologist at the University of York.

“The silver lining, if we can call it that, is this allows for historians and archaeologists to come in and uncover more of its history than we ever knew before. It is a palimpsest of layers of history, and we can come in and understand the craft of our medieval forebears.”

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Casert reported from Strasbourg, France. Angela Charlton in Paris and Gregory Katz in London contributed to this story.

Story: Jill Lawless and Raf Casert

The world reacted with shock and prayers to the massive fire at the Notre Dame Cathedral in Paris, united in grief and in solidarity with the people of France.

As the flames tore through the 12th-century cathedral, Spain’s prime minister offered France the help of his country in the recovery.

The fire is a “catastrophe for France, for Spain and for Europe,” Spanish Prime Minister Pedro Sánchez tweeted Monday, adding that the flames are destroying “850 years of history, architecture, painting and sculpture.”

French President Emmanuel Macron told reporters near the scene that he will seek international help, including from the “greatest talents” in the world, to rebuild Notre Dame.

President Donald Trump, speaking at an appearance in Minnesota, spoke of the “terrible, terrible fire” that devastated “one of the great treasures of the world.”

“It’s a part of our growing up, it’s a part of our culture, it’s a part of our lives,” Trump said of the landmark.

Read: Thai Princess, Junta Leader Express Condolences after Notre Dame Fire

The Notre Dame Cathedral, situated on an island in the Seine River in the heart of Paris, is one of the world’s most visited tourist destinations, drawing some 13 million people each year. The fire’s emotional impact was widely felt. People from all over described in Facebook posts how they cried when they heard about the fire.

Former President Barack Obama posted an old photo of himself, his wife Michelle and their two daughters lighting candles in the cathedral.

“Notre Dame is one of the world’s great treasures, and we’re thinking of the people of France in your time of grief,” Obama said on Twitter. Michelle Obama, who was in Paris on Monday on a book tour, said “my heart aches with the people of France.”

“The majesty of Notre Dame – the history, artistry, and spirituality – took our breath away, lifting us to a higher understanding of who we are and who we can be,” she tweeted. She predicted the cathedral would rise again.

Japan’s government early Tuesday expressed sympathy and said it would consider sending support to the French government. “Its damage is a loss to the world and our hearts ache,” said Yoshihide Suga, the chief cabinet secretary.

The Vatican said Pope Francis “has seen with shock and sadness the news of the terrible fire.”

As the flames spread, Cardinal Timothy Dolan, the archbishop of New York, prayed at St. Patrick’s Cathedral in Manhattan for intercession.

“God preserve this splendid house of prayer, and protect those battling the blaze,” Dolan said in a statement.

Paris Mayor Anne Hidalgo said many works of art and holy objects inside the church had been saved, but the art world was distressed about what might have been lost.

Barbara Drake Boehm, senior curator at the Metropolitan Museum of Art’s medieval Cloisters branch in New York, was desolate about damage to the cathedral, which she called “one of the great monuments to the best of civilization.”

“Civilization is just so fragile,” Boehm told a reporter in a trembling voice. “This great hulking monument of stone has been there since 1163. It’s come through so many trials.”

Jeff Ament, bass player for Pearl Jam, remembered spending hours at the cathedral in his first visit, in 1991, with record executive Michael Goldstone.

“Thinking about Paris,” Ament tweeted, with photos of the cathedral.

U.N. Secretary-General Antonio Guterres tweeted that he’s “horrified,” calling the cathedral “a unique example of world heritage.”

In Russia, the Russian Orthodox Church’s secretary for inter-Christian relations Hieromonk Stefan called the fire “a tragedy for the entire Christian world and for all who appreciate the cultural significance of this temple,” the state news agency RIA-Novosti reported:

On Twitter, Trump suggested using planes to drop water on the flames. France’s Civil Security agency said that wasn’t feasible.

“All means are being used, except for water-bombing aircrafts which, if used, could lead to the collapse of the entire structure of the cathedral,” the agency tweeted.

Story: Andrew Selsky