In the wake of the devastating fire that tore through the roof of Notre-Dame cathedral and destroyed its iconic spire, international attention quickly turned to the future of the iconic Paris landmark. Donations poured in for the clean-up and reconstruction of the 850-year-old Gothic structure, from both small donors and major companies and foundations. An international competition was launched for the redesign of Notre-Dame’s spire, with the French Senate ultimately voting that the cathedral should be restored to its “last known visual state.” French President Emmanuel Macron said that he hopes to see Notre-Dame rebuilt within five years—a timeline that architectural experts have called “unrealistic.”

But now, the cathedral’s rector has raised doubts as to whether Notre-Dame will be salvaged at all. Monsignor Patrick Chauvet tells Jeffrey Schaeffer and Angela Charlton of the Associated Press that the historic building is so fragile there is a “50 percent chance” it cannot be saved.

The 50,000 tubes of scaffolding that had been installed at Notre-Dame before the April fire to facilitate renovation work pose a major obstacle to the restoration process. These tubes welded together during the inferno, forming a “mass of twisted metal of roughly 250 tons that is weighing down on the structure,” writes Aurelien Breeden of the New York Times.

The scaffolding has to be removed to make the building safe for restoration, Chauvet says—but accomplishing this task is no mean feat. Three levels of steel beams will first have to be placed around the exterior of the building, forming a “stabilizing belt,” writes Francesco Bandarin, an architect and former senior official at UNESCO, for the Art Newspaper. Next, “telescopic crawler cranes ... will allow roped technicians to descend into the forest of pipes and gradually cut them away after having coated them with a protective layer to avoid spreading the pollution caused by the melting of the lead roof.”

This work is expected to be completed by next April, according to Bandarin. But Chauvet says it is unclear whether the scaffolding can be removed without causing further damage to Notre-Dame. “Today we can say that there is maybe a 50 percent chance that it will be saved,” he tells Schaeffer and Charlton. “There is also a 50 percent chance of scaffolding falling onto the [building’s] three vaults.”

These vaults, or arches, are vital to keeping the cathedral stable, now that its roof has been compromised. And there are other threats to the building’s future. In areas where Notre-Dame’s roof and vaults collapsed completely, hanging beams are at risk of falling down and damaging the cathedral, Bandarin writes. The fire also released billows of toxic lead dust into the atmosphere, not only posing serious health concerns, but also causing delays to the repairs process.

Things are not looking entirely bleak, however. Temporary supports have reinforced Notre-Dame's 28 flying buttresses, and measurements taken in different parts of the building “have provided encouraging results, indicating that the overall structural system is stable,” writes Bandarin. Vaulting above the cathedral’s north transept was also found to be structurally sound.

Even if Notre-Dame can be rescued, it is unlikely that it will be accessible to the public in the near future. Chauvet estimates after the scaffolding is removed it will be three years before people can safely enter the landmark, and that the complete restoration will take even longer. Religious services have been relocated to Saint-Germain l’Auxerrois, a Gothic church near the Louvre; this Christmas, for the first time in more than two centuries, Notre-Dame did not host a Midnight Mass.

If experts are able to successfully remove the scaffolding from the cathedral, those who are anxiously monitoring Notre-Dame’s fate will be able to breathe a sigh of relief. But at the moment, Chauvet tells Schaeffer and Charlton, Notre-Dame “is not out of danger.”