As French firefighters battle to save what remains of the historic Notre Dame Cathedral, questions are being asked about the cause of the inferno.
Here's what we know so far.
The blaze started at about 6.50pm local time on Monday night - 2.50am AEST. A spokesman for the cathedral told local media the fire alarm went off almost immediately.
Smoke could be seen coming from the building's attic and pictures and video of the fire were being shared around the world on social media within minutes.
Horrified viewers watched in real time as the iconic gothic structure's main spire collapsed as about 400 firefighters battled the flames.
French firefighters said the cause of the blaze was not immediately clear but was "potentially linked" to ongoing renovations at the 850-year-old monument.
Police have launched an investigation into the fire, which is reported to be focusing on an "involuntary" cause rather than a criminal act.
City prosecutor Remy Heitz said late Monday night it was "too early" to determine the cause but that the preliminary investigation suggested the blaze was started accidentally.
"Everything will be put in place to determine the origin of the fire," government Minister Laurent Nunez told local media from the scene.
ARSON CLAIMS SHUT DOWN
While officials appear to have ruled out arson, the Notre Dame fire comes amid a spate of attacks on Catholic churches in France since the start of the year.
Last month the Church of St Sulpice in Paris was set on fire in a suspected arson attack. Other churches across the country have seen crosses and statues smashed and smeared with human faeces.
Ellen Fantini from the Observatory of Intolerance and Discrimination Against Christians in Europe told Newsweek there was a "rising hostility in France against the church and its symbols".
The Vienna-based group said there had been a 25 per cent increase in attacks on Catholic churches in the first two months of the year compared with 2018.
"The pressure is coming from the radical secularists or anti-religion groups as well as feminist activists who tend to target churches as a symbol of the patriarchy that needs to be dismantled," Ms Fantini told the publication last month.
As the blaze was unfolding, a controversial French media commentator was cut off by Fox News host Shep Smith for suggesting the Notre Dame blaze was intentionally lit.
"Everybody's really under shock now in France," Philippe Karsenty told the channel. "I would tell you something. Even if nobody died, it's like a 9/11, it's a French 9/11. It's a big shock. This church was there for more than 850 years. Even the Nazis didn't dare to destroy it."
He added, "You need to know that for the past years, we've had churches desecrated each and every week in France, all over France. So, of course, you will hear the story of the politically correct - the political correctness which will tell you it's probably an accident."
Smith immediately ended the phone call. "We are thousands of miles away and the man on the phone with us has absolutely no information of any kind about the origin of this fire and neither do I," he told viewers.
"The fire investigators will at some point come to a determination about what caused this and conspiracy theories about anything are worthless and in many cases counter productive and injurious to society. And those who entertain them are not acting in the best interests of the people of this planet."