Patrick Chauvet, the Notre Dame rector, told French radio that the cathedral's "fire watchers" were on constant lookout and three times each day made "assessments" in the vulnerable area under the wooden roof.
The prosecutor's office said police had started questioning construction workers who had been carrying out extensive renovations to balustrades and crumbling gargoyles at the site.
- A huge fire swept through the roof of the famed Notre-Dame Cathedral in central Paris on April 15, 2019, sending flames and huge clouds of grey smoke billowing into the sky.
In an evening address to the nation, President Emmanuel Macron described the firefighters as heroic and said he hoped the country would reconstruct Notre Dame within five years - a shorter timetable than that put forward by experts.
"All the 18th-century steles, the pietas, frescoes, chapels and the big organ are fine", he said.
A clear view to the sky can be seen through the space that once held St. Boniface Cathedral's large stained-glass window.
"Our Lady of Paris in flames", Macron said, "I am sad tonight to see this part of us burn". He said the restoration work will have to use new technology to rebuild the roof.
"Those trees had been saplings in the 10th century, they were mature trees by the 12th century when they were felled".
"This is terrible for them", said Mulaire.
But Mr Philippe posed the question of "whether we should even recreate the spire as it was conceived by [French architect] Viollet-le-Duc. or if, as is often the case in the evolution of heritage, we should endow Notre-Dame with a new spire". "But perhaps it can't be recreated as it was". The only major work damaged inside was the cathedral's high altar, installed in 1989 under Cardinal Jean-Marie Lustiger.
With the beloved cathedral partially in ruins, tens of thousands lined the Seine to observe the historic moment - a masterpiece of gothic architecture forever changed.
"It's a very deep sadness". Feydeau told France Info radio that the cathedral's roof can not be rebuilt exactly as it was before the fire because "we don't, at the moment, have trees on our territory of the size that were cut in the 13th century".
"We need to remind people of how France, and Europe, have recovered from other tragedies-the rebuilding after the World Wars for example", Maude said. "It was hard to imagine this could ever happen". "I'd say decades", said Eric Fischer, head of the foundation in charge of restoring the 1,000-year-old Strasbourg cathedral.
Winnipegger Mariette Mulaire, the president and CEO of the World Trade Centre, an organization which works to help Manitoba companies grow their businesses internationally, has visited Paris several times and has toured the Notre Dame Cathedral.
One of the group's members, Ron Ivey, said he was "heartbroken".
Judging by the comments on her post, it seems many people saw the same thing.