Open this photo in gallery In this April 15, 2019, file photo, people watch as flames and smoke rise from Notre-Dame cathedral in Paris. Thibault Camus/The Associated Press

A “computer glitch” may have been behind the fast-spreading fire that ravaged Notre-Dame, the cathedral’s rector said on Friday, as architects and construction workers tried to figure out how to stabilize the damaged structure and protect it from the elements.

The fire burned through the lattice of enormous oak beams supporting the monument’s vaulted stone ceiling, dangerously weakening the building. The surrounding neighbourhood has been blocked off, and stones have continued to tumble off the sides of the cathedral since Monday evening’s devastating blaze.

Speaking during a meeting of local business owners, rector Patrick Chauvet did not elaborate on the exact nature of the glitch, adding that “we may find out what happened in two or three months.”

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On Thursday, Paris police investigators said they think an electrical short-circuit most likely caused the fire.

The Parisien newspaper has reported that investigators are considering whether the fire could be linked to a computer glitch or related to temporary elevators used in the renovation that was under way at the time the cathedral caught fire. Mr. Chauvet said there were fire alarms throughout the building, which he described as “well protected.”

Charlotte Hubert, president of a group of French architects who specialize in historic monuments, told BFM television that experts plan to spread a custom-made peaked tarpaulin across the cathedral’s roof, with enough space to also shield workers rebuilding the frame.

French President Emmanuel Macron is expected to set out reconstruction ideas during meetings on Friday with officials from the United Nations’ cultural agency, UNESCO.

Mr. Macron is moving quickly on the fire-ravaged monument’s reconstruction, which is being viewed both as a push to make it part of his legacy and a way to move past the divisive yellow vest protests over economic issues in France.

Notre-Dame’s reconstruction is prompting widespread debate across France, with differing views emerging over whether it should involve new technologies and designs. Mr. Macron’s office has, for example, said the President wants a “contemporary architectural gesture to be considered” for the collapsed spire, which wasn’t part of the original cathedral.

Mr. Macron hasn’t offered any specifics on his vision for the roof or whether the frame should be wood, metal or concrete, according to his cultural heritage envoy, Stephane Bern. He has named a general, Jean-Louis Georgelin, former chief of staff of the armed forces, to lead the reconstruction effort.

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More than $1-billion has already poured in from people from all walks of life around the world to restore Notre-Dame.

Judith Kagan, a conservation official at France’s Culture Ministry, said the artworks inside Notre-Dame had suffered no major damage from the fire and the pieces were being removed from the building for their protection.

The Notre-Dame fire delayed Mr. Macron’s long-awaited plans to quell anti-government protests that have marred his presidency. The French leader abandoned a planned TV address to the country on the evening of the fire, heading to the scene instead and declaring: “We will rebuild Notre-Dame.”

According to an opinion poll by BVA institute published on Friday – the first carried out since the fire – Mr. Macron has gained three points in popularity in the past month with an approval rating of 32 per cent. That advance puts him back at the support level of September, before the yellow vest crisis, BVA said.

Although all French polls show that Mr. Macron’s popularity has remain depressed since a tax increase on retirees last year, they suggest his party may be ahead in France’s May 26 European Parliament election, with Marine Le Pen’s far-right party, the National Rally, close behind.

Mr. Macron is now expected to detail his new measures next week. Mr. Macron earlier was planning to respond to demonstrators’ concerns over their loss of purchasing power with tax cuts for lower-income households and measures to boost pensions and help single parents.

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Despite the destruction of Notre-Dame dominating the news in France, a new round of yellow vest protests is planned on Saturday across the country, including in Paris.

In a hopeful development on Friday, 180,000 bees being kept in hives on Notre-Dame’s lead roofing were discovered alive.

“I am so relieved. I saw satellite photos that showed the three hives didn’t burn. I thought they had gone with the cathedral,” said Nicolas Geant, the monument’s beekeeper.

Mr. Geant has looked after the bees since 2013, when they were installed as part of a citywide initiative to boost declining bee numbers.

Since the insects have no lungs, Mr. Geant said the carbon dioxide in the fire’s heavy smoke put the bees into a sedated state instead of killing them. He said when bees sense fire they “gorge themselves on honey” and protect their queen. He said European bees never abandon their hives.