PARIS — Investigators are converging around two theories of what caused last week’s devastating fire at Notre-Dame cathedral: a short-circuit near its spire, possibly caused by electrified bells, or negligence by workers carrying out renovations, a theory fueled by the discovery of cigarette butts.
On Thursday, for the first time, police investigators were allowed to search the cathedral’s vast interior for clues, said a police official who was not authorized to speak to the news media and requested anonymity.
The investigators had been prevented from going into the cathedral before Thursday because of concerns about the stability of the damaged structure, whose stone was weakened in the intense heat, the official said.
More than a week after the catastrophic fire shook France and gripped the world, toppling the cathedral’s spire and leading to an outpouring of support, investigators are still seeking a cause of the blaze.
The official said that so far nothing was being ruled out and that the investigation could last several weeks. It was being complicated by the intensity of the blaze, as well as by the tons of water used by firefighters to put it out, both of which destroyed evidence.
But the official said that the investigators had already interrogated dozens of individuals, including workers, company officials, cathedral staff, architects and others in the local government.
So far attention has focused on a number of electrical installations near the spire, including a series of six midsize bells, according to officials with knowledge of the complex interplay of elements that existed until 10 days ago at the church summit.
The police have also found cigarette butts on the scaffolding — a possible explanation for the blaze, though one strongly disputed by a spokesman for the company that erected it. Restoration work had begun at the church before the fire, and much of the building was sheathed in scaffolding.
The police official confirmed, however, that smoking — forbidden under company rules — was being considered as a cause, among others.
Yet already looming as a backdrop for the investigation was a conflict that routinely plays out in efforts to preserve France’s vast catalog of historic monuments: tradition against modernity.
Notre-Dame’s contemporary custodians — its architects, priests and caretakers — wanted to preserve the structure’s medieval essence. But over the years they made a number of concessions that ultimately might have threatened it, including electrifying the two sets of bells, originally installed by the 19th-century architect Eugène Viollet-le-Duc, who gave Notre-Dame a vast face-lift.
The architect in charge of Notre-Dame until 2013, Benjamin Mouton, had warned in 2010 against installing lights amid the beams because of the area’s “combustion potential” and the “fire risk” such lights posed, according to notes preserved in the state archives related to historical monuments.
Yet the bells at the top of the cathedral — three in the spire and, beneath it, three in the vast attic of ancient interlaced beams known as the forest — were electrified in any case in two stages in 2012 and 2007.
The vast majority of church bells in France, to be sure, are electrified. But only Notre-Dame had the forest — there was no comparably complex assemblage of ancient dried wood, some dating to the 13th century.
Anything similar had already burned, experts said, and on the night of April 15, Notre-Dame’s beams, too, joined that destiny.
“That the fire started in the bells — that is pertinent, and plausible,” said Régis Singer, a bells specialist at the Ministry of Culture who wrote a report on the electrification of the spire bells.
Nicolas Gueury, who electrified the other set of bells, in 2007, quickly ruled the idea out in an interview this week, while conceding, ‘‘Of course, I’ve thought about it.”
Mr. Gueury, now retired, worked for Mamias, a company that for decades has made a specialty out of electrifying church bells in France.
“For me, this would be impossible,” he said, adding that a sizable catalog of safeguards against dysfunction — circuit breakers, shielding — were installed at the same time. “It was draconian. We tripled the precautions,” he said.
“We were all hyper-prudent. You don’t do just anything in the forest,” he said. “It was hyper-securitized.”
“There was a real kind of delirium about it,” he said. “So much so, that we thought about dropping the whole project.”
He did not, however.
He pointed out that if a short-circuit had occurred, it could have done so only at the moment when the bells were being sounded — at the moment when the priest celebrating mass pushed a button, sending electricity to the bells above.
On the night of April 15, Mr. Gueury’s bells had not yet rung by the time of the first fire alarm, at 6:21 p.m., but five minutes later.
The bells in the spire had sounded, however, at 6:04 p.m., as they always did to announce the Mass at 6:15. Those bells worked on the same principle — they were set off by an electric impulse.
Another hypothesis being considered is possible negligence of workers at the site. That theory has gained in plausibility since the discovery by the police of cigarette butts on the scaffolding.
Three days before the fire broke out, at least one worker was observed smoking while on the scaffolding, according to a French official with knowledge of the situation, who spoke on condition of anonymity, citing the sensitivity of the matter.
A spokesman for the scaffolding company said Thursday: “Workers might have smoked at the worksite outside, and we regret it.’’
The spokesman added, however, that the workers “did not go into the attic on the day of the fire.’’
‘‘A cigarette could not have caused the fire,’’ he insisted.
The last worker left and switched off the electric fuse box for the scaffolding at 5:50 p.m., 30 minutes before the alarm sounded in the cathedral, and the public was evacuated a first time, only to be called back in minutes later.
But some few minutes before that alarm, security workers at the cathedral had received a visual alert of a problem in the attic from their system’s detectors, according to Elytis, the company in charge of fire security.
It wasn’t until some 40 minutes later that the first firefighters arrived, nine minutes after they got the call.
Mr. Mouton’s 2010 musings about the advisability of a much quicker response to potential fire, preserved in the archives, appear all the more prescient:
“The call to security services — must it be conditional on the lifting of all doubts?’’ he wrote. ‘‘In the case of the sensitive zones, like the summit and the towers, can one take the risk of waiting 15 minutes before calling for help? Isn’t a false alarm to the fire department better than a fire?”
Source : Nytimes
