People walk on the Seine river banks, near Notre Dame cathedral, in Paris, Wednesday, Dec. 25, 2019. The rector of Notre Dame Cathedral says the Paris landmark is still so fragile that there's a "50% chance" it might not be entirely saved, because scaffolding installed before this year's fire is threatening the vaults of the Gothic monument. (AP Photo/Thibault Camus)

PARIS— The rector of Notre Dame Cathedral says the Paris landmark is still so fragile that there’s a “50% chance” the structure might not be saved, because scaffolding installed before this year’s fire is threatening the vaults of the Gothic monument.

Monsignor Patrick Chauvet said restoration work isn’t likely to begin until 2021 — and described his “heartache” that Notre Dame couldn’t hold Christmas services this year, for the first time since the French Revolution.

“Today it is not out of danger,” he told The Associated Press on the sidelines of Christmas Eve midnight Mass in a nearby church. “It will be out of danger when we take out the remaining scaffolding.”

“Today we can say that there is maybe a 50% chance that it will be saved. There is also 50% chance of scaffolding falling onto the three vaults, so as you can see the building is still very fragile,” he said.

The 12th-century cathedral was under renovation at the time of the accidental April fire, which destroyed its roof and collapsed its spire. With no more roof to keep the massive stone structure stable, the cathedral’s surviving vaults are crucial to keeping it standing, but they are vulnerable.