Notre Dame de Paris is not yet saved, the military general overseeing the restoration of the landmark after April's devastating fire warned on Sunday.

There is still a risk that the cathedral's vaulted ceilings might collapse.

General Jean-Louis Georgelin said Notre Dame is "still in a state of peril" after the fire that destroyed its roof and its spire on April 15.

"Notre Dame is not saved", he said on French television. "There is an extremely important step ahead, which is to remove the scaffolding that had been built around the spire", he said.

The scaffolding had been in place before the fire, as the cathedral was undergoing renovations.

Georgelin is not the only one to worry. Notre Dame's rector, Monsignor Patrick Chauvet, told the Associated Press last month that the landmark building is still so fragile there's "a 50% chance" that the scaffolding may fall on the vaulted ceilings, which would threaten the structure.

Georgelin, a former chief of staff for the French army, said that the current condition of the vaults is not fully known, which means he could not guarantee that "it won't fall apart".

``"To make sure, we need to inspect them, to remove the rubble that is still on them, it's a very difficult work that we have started,'' he said.

On top of that, the fire released tons of lead dust into the air and the cathedral's surroundings. The lead dust needs cleaning up, which will slow down the reconstruction work.

But "reassuring" observations have been made on the cathedral, Georgelin said, adding he feels "quite confident" in the path to restoration.

The scaffolding on Notre Dame should be removed by mid-2020 and the restoration work should start next year, he said.

French president Emmanuel Macron has said he wants cathedral rebuilt by 2024, for the Paris Summer Olympics. Experts say that time frame is not realistic.

Moreover, according to Georgelin, no decision has been made yet about how the spire and roof should be rebuilt and the material used for it - wood, metal, concrete - has yet to be chosen.

The first stone of Notre Dame was laid in 1163. The spire was added in 1859, and following its destruction in the inferno Macron announced an international architecture competition to design a new spire.

Georgelin said the competition will take place later this year, but didn't rule out having the new spire built exactly like the old one.

``"Only after that (competition), when the choice has been made, we will be able to rebuild the spire,'' he said.