INVESTIGATORS think an electrical short-circuit was the most likely cause of the Notre Dame Cathedral fire, according to a French judicial police official.
The official said investigators still do not have the green light to work in the cathedral and search in the rubble for safety reasons.
He said the monument is still being consolidated with wooden planks to support some fragile parts of the walls.
The probe was taking place as France paid a day-long tribute to the Paris firefighters who saved the famous cathedral from collapse and rescued its treasures.
The tributes came as construction workers rushed to secure an area above one of the church's famed rose-shaped windows and other vulnerable sections of the fire-damaged landmark.
President Emmanuel Macron held a ceremony at the Elysee Palace to thank the hundreds of firefighters who battled the fast-moving fire at Notre Dame for nine hours, preventing the structure's destruction and rescuing many of the important relics held inside.
"We've seen before our eyes the right things perfectly organised in a few moments, with responsibility, courage, solidarity and a meticulous organisation", Mr Macron said. "The worst has been avoided."
Mr Macron said the firefighters will receive a medal for their courage and devotion.
The huge cathedral, including the spire that was consumed by flames and collapsed, was in the initial stages of a lengthy restoration.
The roof was destroyed, but Notre Dame's famous bell towers, rose windows, organ, and precious artworks were saved.
Fire officials warned the building remains very fragile and extremely dangerous for construction workers, restoration experts and neighbours.
Police, citing "important risks" of collapse and falling objects, officially closed a large swathe of the island in the Seine River on which Notre Dame sits. The area had been unofficially blocked off since the fire.
Workers using a crane were removing some statues to lessen the weight on the cathedral's fragile gables, or support walls, and to keep them from falling, since the section lacked the support of the massive timber roof that burned in the devastating blaze.
They were also securing the support structure above one of Notre Dame's rose windows with wooden planks.
Remarkably, no one was killed in the fire, which began during a Mass, after firefighters and church officials speedily evacuated those inside.
Among the firefighters honoured was Paris fire brigade chaplain Jean-Marc Fournier, who said he was falsely credited with helping salvage the crown of thorns believed to have been worn by Jesus at his crucifixion.
The chaplain said a team of rescuers broke the relic's protective covering and an official who had the secret code to unlock the protection finished the job.
Among others honoured was Myriam Chudzinski, one of the first firefighters to reach the roof as the blaze raged.
Loaded with gear, they climbed hundreds of steps up the cathedral's narrow spiral staircase to the top of one of the two towers. She had trained at the site for hours for just this moment.
"We knew that the roof was burning, but we didn't really know the intensity," she told reporters. "It was from upstairs that you understood that it was really dramatic. It was very hot and we had to retreat, retreat. It was spreading quickly."
Investigators so far believe the fire was accidental, and are questioning both cathedral staff and workers who were carrying out renovations. Some 40 people had been questioned by Thursday, according to the Paris prosecutor's office.
The building would have burned to the ground in a "chain-reaction collapse" had firefighters not moved as rapidly as they did to battle the blaze racing through the building, said Jose Vaz de Matos, a fire expert with France's Culture Ministry.
Mr Macron wants to rebuild the cathedral within five years - in time for the 2024 summer Olympics that Paris is hosting - but experts say the vast scale of the work to be done could easily take 15 years, since it will take months, even years, just to figure out what should be done.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules here