The Paris police announced late on Monday night that the fire at the Notre Dame Cathedral was under control.

One firefighter was seriously injured in the fire that broke out Monday evening.

Paris Mayor Anne Hidalgo said on Monday night that firefighters were optimistic that they could salvage the cathedral’s iconic main towers.

Speaking outside the cathedral, fire chief Jean-Claude Gallet had told reporters he was “not sure we are capable of stopping the spreading” to Notre Dame’s second tower and belfry, but he later said they had indeed been successful in stopping it from spreading to the northern belfry of the 850-year-old building.

French President Emmanuel Macron said the "worst has been avoided" in the fire and added, “We will rebuild Notre Dame”. He also said he would launch an international fundraising campaign for the restoration of the cathedral.

The blaze collapsed the cathedral’s spire and had spread to one of its landmark rectangular towers. The 12th-century cathedral is home to incalculable works of art and is one of the world’s most famous tourist attractions, immortalized by Victor Hugo’s 1831 novel “The Hunchback of Notre Dame.”

The cause of the blaze was not known, but The Associated Press quoted the Paris fire brigade as saying the fire is “potentially linked” to a 6 million-euro renovation project on the church’s spire and its 250 tons of lead.

Prosecutors have opened an investigation into the cause of the fire.

Last year, the Catholic Church in France launched an urgent appeal for funds to save the cathedral, which was starting to crumble.

US President Donald Trump tweeted earlier, “So horrible to watch the massive fire at Notre Dame Cathedral in Paris. Perhaps flying water tankers could be used to put it out. Must act quickly!”

French President Emmanuel Macron was treating the fire as a national emergency, rushing to the scene and straight into meetings at the Paris police headquarters nearby.

Acting Foreign Minister Yisrael Katz said on Monday evening, "On behalf of the State of Israel, I would like to express my deepest solidarity with France and the French nation over the terrible fire at Notre Dame, a world symbol of civilization."

Foreign Ministry Spokesman Emmanuel Nahshon wrote in French about the fire at Notre Dame Cathedral on Twitter.

"Les mots manquent pour décrire le sentiment de choc et de consternation. Notre plus profonde solidarité avec les Français et particulièrement les Parisiens."

(Words cannot describe our feeling of shock and consternation. Our deepest solidarity with the French and especially the Parisians.)