PARIS — A large fire broke out at the Cathedral of Notre-Dame in Paris on Monday evening, causing part of the historic church’s spire to collapse as the blaze spread along its roof.
André Finot, a spokesman for the cathedral, said in a telephone interview that the cause of the fire remained unknown, and there was no immediate indication that anyone had been hurt.
“It’s not about the faith — Notre Dame is a symbol of France,” said Emmanuel Guary, a 31-year-old actor who was among a huge crowd amassed on the Rue Rivoli, on the Right Bank. Many had tears in their eyes.
After part of the spire collapsed, the fire appeared to spread across the rooftop, where the growing flames licked the sky and projected a yellow smoke over the horizon.
The fire alarm first went off around 6:30 p.m., Mr. Finot said, adding that the cathedral had been evacuated. The Paris prosecutor’s office said it had opened an investigation.
As the last rush of tourists were trying to get in for the day, the doors of Notre Dame were abruptly shut without explanation, witnesses said.
Within moments, tiny bits of white smoke started rising from the spire. Billowing out, the smoke started turning gray, then black, making it clear that a fire was growing inside the cathedral, which is currently covered in scaffolding. Soon, orange flames began punching out of the spire, quickly increasing in intensity.
The French police rushed in and started blowing whistles, telling everyone to move back, witnesses said. By then, the flames were towering, spilling out of multiple parts of the cathedral. Tourists and residents alike came to a standstill, pulling out their phones to call their loved ones. Older Parisians began to cry, lamenting how their national treasure was quickly being lost.
Thousands stood on the banks of the Seine river and watched in shock as the fire tore through the cathedral’s wooden roof and brought down part of the spire. Video filmed by onlookers and shared on social media showed smoke and flames billowing from the top of the cathedral.
Vincent Dunn, a fire consultant and former New York City fire chief, said that fire hose streams couldn’t reach the top of such a cathedral, and that reaching the top on foot was often an arduous climb over winding steps.
“These cathedrals and houses of worship are built to burn,” he said. “If they weren’t houses of worship, they’d be condemned.”
Mayor Anne Hidalgo of Paris said on Twitter that “a terrible fire” had struck at the cathedral.
“The Paris firefighters are currently trying to stop the flames,” Ms. Hidalgo said. “I ask everyone to respect the security boundaries.”
Firefighters were on the scene, said Mr. Finot, who was about 70 feet away from the cathedral.
The Paris police warned people to stay away from the area around the cathedral, which is one of the city’s most famous landmarks, drawing about 13 million visitors a year.
Built in the 12th and 13th centuries, the cathedral is currently undergoing extensive renovation work. Last week, several statues were lifted by crane from the spire.
“It hurts to watch this. The cathedral is the symbol, the heart of Paris,” said Pierre-Eric Trimovillas, 32. The crowd gasped and cried in horror as the spire fell, Mr. Trimovillas said, adding, “Paris is beheaded.”
Angelique de Almeida, 32, watched the fire through tears. “We are going to lose her, everything is up in flames,” she said. “We lose this, we lose Paris. It is apocalyptic. And this is the Holy Week.”
President Emmanuel Macron of France canceled a major speech that was scheduled for Monday evening, in which he was supposed to announce measures addressing the Yellow Vest protest movement that has roiled the country over the past months.