Efforts by more than 400 firefighters focused mostly on the north belfry, with Paris' chief firefighter highlighting the risk to what remains of the structure if the main bell should fall through the tower.
Shortly after 11pm, news service AFP reported that firefighters said that they believe Notre-Dame's main structure can be "saved and preserved."
Following a visit to the site, President Emmanuel Macron vowed to restore the cathedral, which belongs to the French government.
"We will rebuild Notre-Dame," Macron said, according to AFP.
Earlier, the French president released a statement on Twitter expressing the "emotion" of "the whole nation."
Macron said his thoughts were with all Catholics and French citizens.
"Like all our compatriots, tonight I am sad to see a part of [all of] us burn."
Archbishop Michel Aupetit of Paris said that "firefighters are still fighting to save the towers of Notre-Dame de Paris. The frame, the roof and the boom are consumed."
"Pray," the archbishop told the priests of Paris, he also invited them to ring church bells as a public invitation to prayer.
Unconfirmed reports indicate that the major religious and artistic treasures of the cathedral were removed as the fire began, including a relic of the crown of thorns.
As flames spread, locals reported buring debris from the fire falling in the immeadite vicinity of the cathedral. By 9pm the fire was contained within the cathedral building itself.
Firefighters cautioned Monday night that although the height of the flames had abated, the fire within the cathedral itself was not yet fully under contol. Efforts were initially hampered by the height of the cathedral roof, which prevented emergency services from reaching the flames.
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No announcement has yet been made concerning any injuries or fatalities resulting from the fire.
Paris mayor Anne Hidalgo issued a series of brief statements via Twitter saying that emergency responders are fighting to control the flames and appealing to local residents to keep the area clear to assist their efforts.
"There is no word strong enough to express my sorrow," Hidalgo said.
Outside the security cordon, Parisian Catholics have gathered in large crowds, kneeling to pray and singing devotional hyms to Our Lady.
Officials have not yet determined what caused the fire, which is still burning. Both the fire department and the office of the public prosecuter in Paris have confirmed that invesitgations into the origin and cause of the fire have been opened.
Built between the twelfth through fourteenth centuries, the landmark cathedral in the French capital is one of the most recognizable churches in the world, receiving more than 12 million visitors each year.