After hours of battling a “significant fire” that broke out at the iconic Notre Dame Cathedral in central Paris at 7 pm local time, firefighters were able to bring it under control in the early hours of Tuesday.

“The fire is completely under control. It is partially extinct, only residual fires were still burning,” said the Paris spokesman Gabriel Plus.

NBC journalist Nancy Ing reported that gargoyles were falling off the roof.

Both the spire and roof of the cathedral collapsed, but the main structure was preserved, Paris fire chief Jean-Claude Gallet told reporters at the scene.

“We now believe that the two towers of Notre-Dame have been saved,” he added.

Gallet said that the operation was focused on preserving the rear of the cathedral where the most valuable works are located.

There was still a risk that some of the interior structures could collapse, and firefighters would work overnight to cool them down, he said.

One firefighter was seriously injured in the blaze — the only reported casualty.

The cause of the fire was not immediately known. The Paris Prosecutor has opened an official investigation to determine the cause of the fire.

An investigation was opened for accidental destruction by fire, said Paris prosecutors.

French President Emmanuel Macron pledged to rebuild Notre-Dame in a public address.

“Notre-Dame is burning, and I know the sadness, and this tremor felt by so many fellow French people. But tonight, I’d like to speak of hope too,” he said, announcing the launch of a fundraising campaign.

“Let’s be proud, because we built this cathedral more than 800 years ago, we’ve built it and, throughout the centuries, let it grow and improved it. So I solemnly say tonight: we will rebuild it together,” he added.

Macron also thanked the emergency services and said his thoughts were with Catholics across France and around the world.

However, the newly elected president of the Bishops’ Conference of France, Eric de Moulins-Beaufort said that restoring the iconic building would take “years of work”.

A French heritage organisation, Fondation du Patrimoine, tweeted that they would launch a “national collection” for the reconstruction of the cathedral.

One of the richest French families, the Pinault family, pledged €100 million for Notre-Dame.

Nicolas Marang, 47, a consultant and a Paris resident for 27 years who witnessed and  took a video of Notre Dame’s spire falling, told Euronews the blaze was “an absolute nightmare”.

“I keep thinking about, all the culture. It is so delicate and now it’s all gone. It’s all burned,” he said.

“People started taking pictures. Some people were crying. It was like being knocked out,” he added.

Onlookers gazed on in disbelief at the inferno at the religious landmark, which is located on the Ile de la Cite, an island in the River Seine.

“A terrible fire is underway at Notre-Dame Cathedral in Paris,” mayor Anne Hidalgo wrote on Twitter. “Firefighters are trying to control the flames … I invite everyone to respect the security perimeter.”

Politicians from across the world tweeted their condolences and support to the French people, while Twitter users shared their memories of visiting Notre Dame in response to the blaze.

Police advised people to avoid the area in a tweet and requested that they facilitate the passage of emergency and vehicles.

A group of 16 copper statues escaped the blaze as they were removed from the cathedral’s roof on April 11 for restoration work, as part of a €6 million rennovation project.

A centuries-old crown of thorns made from reeds and gold, as well as the tunic worn by Saint Louis, a 13th-century king of France, were saved, Notre-Dame’s top administrative cleric, Monsignor Patrick Chauvet said.

Firefighters had struggled to take down some of the large paintings in time, he added.

French President Emmanuel Macron cancelled a planned 8 pm CEST address to the nation on the “gilets jaunes” (yellow vests) movement due to the “terrible fire”, said an official at the president’s Elysee office.