Smoke billows from the Notre Dame Cathedral after a fire broke out, in Paris, France, April 15, 2019. A massive fire consumed Notre-Dame Cathedral on Monday, gutting the roof of the Paris landmark and stunning France and the world, though firefighters saved the main bell towers and outer walls from collapse before bringing the blaze under control. REUTERS/Julie Carriat

Smoke billows from Notre Dame Cathedral after a fire broke out, in Paris, France April 15, 2019. Flames that began in the early evening burst rapidly through the roof of the eight-centuries-old cathedral and engulfed the spire, which toppled, quickly followed by the entire roof. REUTERS/Charles Platiau

Smoke billows from Notre Dame Cathedral after a fire broke out, in Paris, France April 15, 2019. The fire, after burning for about 8 hours, was largely extinguished by 0300 CET on Tuesday. Earlier, in addition to battling to prevent one of the main bell towers from collapsing, firefighters tried to rescue religious relics and priceless artwork. One firefighter was seriously injured - the only reported casualty. REUTERS/Charles Platiau

Smoke billows as fire engulfs the spire of Notre Dame Cathedral in Paris, France April 15, 2019. A massive fire consumed Notre-Dame Cathedral on Monday, gutting the roof of the Paris landmark and stunning France and the world, though firefighters saved the main bell towers and outer walls from collapse before bringing the blaze under control. REUTERS/Benoit Tessier

Smoke billows from Notre Dame Cathedral after a fire broke out, in Paris, France April 15, 2019. Flames that began in the early evening burst rapidly through the roof of the eight-centuries-old cathedral and engulfed the spire, which toppled, quickly followed by the entire roof. REUTERS/Charles Platiau

People watch from a bridge as smoke billows and fire engulfs the spire of Notre Dame Cathedral in Paris, France April 15, 2019. The fire, after burning for about 8 hours, was largely extinguished by 0300 CET on Tuesday. Earlier, in addition to battling to prevent one of the main bell towers from collapsing, firefighters tried to rescue religious relics and priceless artwork. One firefighter was seriously injured - the only reported casualty. REUTERS/Benoit Tessier