PARIS, April 18 (Xinhua) -- France on Thursday paid a day of tribute to hundreds of firefighters who had put their lives at risk to douse a blaze which devastated Paris' Notre Dame Cathedral, one of the country's landmark symbols.

Thousands of people and many elected officials were gathered in front of Paris city hall to say "thank you" to "those who helped save Notre Dame Cathedral" and applause their professionalism, bravery and determination to save the 12th-century cathedral's structure.

"Thank you to Paris firefighters, who saved, at the risk of perishing, a part of us. We have seen your boundless courage, your unwavering determination," Paris mayor Anne Hidalgo said.

Over 400 firefighters took part in the 15-hour battle to contain the fire that engulfed the centuries-old roof and sent the burnt towering spire through the ceiling.

Despite having some trouble to put out the flames due to the building's height, the firefighters succeeded after long hours to stop the fire's spread to the two bell towers, prevent their collapse and save the artwork at the back of the cathedral.

"We will all remember April 15, 2019. The place where we were. The people we were with. But above all, the heroism of our firefighters who saved, that night our Dame and with it 8 centuries of our history," Interior Minister Christophe Castaner said.

At the Elysee Palace, President Emmanuel Macron received 250 firefighters to express France's "pride" of their "exemplary" response to contain the blaze.

"Nobody will forget the first minutes. France, stunned, sees the spire of Notre Dame collapse. And immediately, they take all the risks to save what can be," he said.

"In memory of this night, they will receive the Gold Medal for an act of courage and dedication," he added in a Twitter message.

Local media reported that the fire, which broke out on Monday evening may be linked to renovation works.

According to Paris prosecutor Remy Heitz, there was no sign of criminal purpose and it was likely to have been the result of an accident. Some 50 people were working on what would be "a long and complex investigation".

The cathedral, whose construction began in 1160 and continued over a century, is part of the World heritage site of "Paris, Banks of the Seine" inscribed on the World Heritage List in 1991.

Notre Dame, one of the finest examples of French Gothic architecture, draws 13 million visitors annually.