The Paris Fire Brigade has tweeted that the stone construction of the cathedral has been "saved," as have the "main works of art" from the building.
In a two-part tweet, the fire service praised the cooperation of "different services" of the state, working together over nine hours to extinguish the inferno at one of Paris' most recognizable landmarks.
"The structure of the cathedral is saved and the main works of art have been put somewhere safe, thanks to the combined action of the different services of the State working together."
"After more than 9 hours of fierce fighting, nearly 400 firefighters from Paris extinguished the appalling fire. 2 policemen and a firefighter were slightly injured," a followup tweet read.
A Twitter user who is in Paris for her honeymoon captured a group of Parisians singing hymns as they walked along a street on the banks of the Seine, close to Notre Dame Cathedral, even as operations to bring the fire under control continued.
The poster, Jordan Doyle, said that she took the video out of her hotel window, a stone's throw from the famed cathedral, in the early hours of Tuesday morning.
"I’m devastated for the people of Paris. I was there on my honeymoon, and I just saw the cathedral for the first time yesterday morning."
She said the singing brought her out of her bed.
"I opened the window and immediately my eyes welled up. It was beautiful to see people coming together for their city and for Notre Dame. You could honestly feel their sadness. It really felt like they were serenading the building."
"They stayed there for a while, singing and applauding. It was surreal."
Laurent Nunez, French Secretary of State to the Ministry of Interior told reporters Tuesday morning that the fire which devastated Paris’ Notre Dame Cathedral Monday was "under control" but has not been completely extinguished.
"There are still small outbreaks, the cooling off process is still underway, new outbreaks were reported and contained right away," he said.
"The risk of fire is now ruled out; now it's about the building, know how the structure will resist to this serious fire last night."
He said that there was a meeting of experts from the French architectural review board "to try and determine if the structure is stable and if the firemen can venture inside and continue their mission."
The Paris Prosecutor’s office tells CNN that investigators have started to hear testimonies from construction workers working on the site.
Parts of the 850-year-old cathedral had been under renovation, but it is as yet unclear whether the upgrade work has a connection to the blaze, which began early Monday evening.
Throughout the city, crowds of residents and tourists hugged one another as the fire raged on Monday evening, some singing hymns.
Others packed the banks of the Seine across from the Gothic masterpiece, hoping against hope that some 400 firefighters could prevent further damage. Still others held their heads in their hands, unable to watch.
While the magnificent edifice with its towers, spire, flying buttresses and stained glass draws tourists, art and architecture buffs from around the world, for generations of Catholics it has also been a place of pilgrimage and prayer.
"This can't be happening, it's breaking my heart," one woman muttered.
"Not Notre Dame. Not Notre Dame."
Read more here.
Notre Dame's centuries-old wooden roof beams, stone exterior and soaring Gothic architecture made Monday's blaze especially difficult to tackle and Paris firefighters deserve praise for their efforts, experts say.
The biggest problem, experts say, was accessing the wooden ceiling beams which formed the frame for the soaring roof.
"It was pretty evident in the first 20 minutes that it was going to be a bad fire," said Gregg Favre, a former firefighter with the St. Louis Fire Department in the United States.
Aerial options like the one suggested by US President Donald Trump were considered unrealistic.
"Perhaps flying water tankers could be used to put it out. Must act quickly!" Trump said in a tweet.
But the French civil security agency, Securite Civile, said in a tweet -- in English, an apparent response to Trump's suggestion -- that any aerial water dumping could "weaken the structure of Notre-Dame and result in collateral damage to the buildings in the vicinity."
The spire and most of the roof of the centuries-old cathedral have been destroyed, but the two bell towers and the main edifice were saved.
Video released by the French Interior Ministry showed the scale of the response. Authorities deployed some 400 firefighters, pumped water from the Seine and flew drones to survey the damage.
Read more here.
While countless workers contributed to the building of the 850-year-old cathedral, every architectural detail refers back to a single overarching design concept.
But, during its construction, there was also considerable scope for individual expression through the structure’s many ornamental carvings.
Their variety provokes almost unfathomable levels of interest, while offering invaluable insight into the way people thought, felt and worked during a crucial period in European history. This playfulness and richness of expression has long been recognized as one of the great hallmarks of Gothic architecture.
Find out more about this historic work of architecture, and why its loss is so tragic, here.
The central Paris cathedral, which celebrated its 850th anniversary in 2013, took 182 years to build -- construction began in the 12th century and was completed in the 13th century -- and can hold more than 6,000 worshipers.
Notre Dame was badly damaged during the French Revolution, and was restored by architect Eugène Viollet-le-Duc in the 19th century. It is known for its enormous stained glass windows, among other remarkable architectural details.
Learn more about this remarkable building here.
Cathy Widawska, who has lived in Paris for 15 years, told CNN that she was walking along the Rue de Rivoli, in the city center near City Hall, when she saw "a little smoke" come from the roof of the cathedral.
She said that she and other Parisians were finding it "very hard today -- (Notre Dame is a) very important monument... it’s very heartbreaking."
"It’s not just about the church, it’s a monument, the identity of people here. It’s the heart and soul of Paris. It’s very hard to see it (burn down)."
"I never thought it would be such a huge fire," she said. "Around 15-20 minutes later, when we could see the flames, it was a very aggressive fire, and when the iconic spire collapsed, it was very hard, everyone who was standing there knew it was very serious."
She said that when she first saw the blaze, her first thought was that it was a terror attack.
"Everyone was terrified, we didn’t really know what was happening." Authorities have since said that they are working under the assumption that the blaze was unintentional.
Widawska told CNN's Don Lemon that it was devastating to see the damage wrought on the centuries-old structure.
"Everyone was very sad, people started to cry, it was a very emotional moment," she said.
"It was like losing someone, you have seen on the faces of people it was like fear and sadness, they know something very bad was happening."