A “significant fire” broke out at the iconic Notre Dame Cathedral in central Paris at 7 pm local time, according to the national police.
Smoke could be seen billowing out from the top of the medieval cathedral, as flames leapt out beside its two bell towers.
NBC journalist Nancy Ing reported that gargoyles were falling off the roof.
Both the spire and roof of the cathedral collapsed, but the main structure was preserved, Paris fire chief Jean-Claude Gallet told reporters at the scene.
“We now believe that the two towers of Notre-Dame have been saved,” he added.
There was still a risk that some of the interior structures could collapse, and firefighters would work overnight to cool them down, he said.
One firefighter was seriously injured in the blaze — the only reported casualty.
The Paris Prosecutor has opened an official investigation to determine the cause of the fire.