Notre Dame cathedral fire: The moment the spire collapsed

The raging fire engulfing the Notre Dame Cathedral has caused the spire of the famed building to collapse.

Consumed by flames, the spire leaned to one side and then collapsed onto the burning roof.

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A spokesman said the entire wooden frame of the cathedral would likely come down, and that the vault of the edifice could be threatened too.

"Everything is burning, nothing will remain from the frame," Notre Dame spokesman Andre Finot told French media.

Melbourne tram driver David White is in Paris with his partner and described the moment the spire collapsed.

"We actually saw from where we were part of the spire that fell," he told Today.

"And straight after the spire fell, the sky virtually went not black but the scene around the towers - the bell towers really darkened.

"The smoke went black. It was just - I can't describe it.

"I have never seen anything like it back home."

Mr White said the city ground to a halt as people watched the landmark burn.

"People were just stopping in cars," he said.

"The emergency authorities that were crossing the bridge in their vehicles were actually filming and taking photos of what they were seeing. It was just shock."

The cause of the blaze is not yet known but the cathedral is undergoing a six million-euro (A$9.4m) renovation project and the spire was surrounded by scaffolding.

With AP, CNN