(CBS)- Notre Dame Cathedral was undergoing $6.8 million in renovations on the church's spire and its 250 tons of lead when a massive fire engulfed the Paris landmark on Monday.
Paris police said the cause of the blaze at the 12th-century cathedral was unknown, but the fire was "potentially linked" to the renovation work being carried out at the site, French media quoted the Paris fire brigade saying.
The cathedral, which is visited by 13 million people per year, was undergoing renovations after cracks began to appear in the stone, sparking fears the structure could become unstable.
"CBS This Morning" reported on the renovation in March 2018. At the time, Michel Picaud, president of the Friends of Notre-Dame of Paris Foundation, took CBS News' Roxana Saberi on the roof of the cathedral to show her walls chipping, stones stapled together and Gothic gargoyles used to drain rain replaced with plastic pipes.
Years of rain, snow and pollution were eroding the flying buttresses that prop the cathedral up, said Picaud, and that was putting the whole cathedral at risk of falling down.
In the backyard of the cathedral there were stones that had either fallen off the structure or were at risk of falling off. There were hundreds of them piled up, in the hopes they can be fixed and put back. But the Archdiocese of Paris said it can't afford all the repairs, which was estimated at $185 million.
The French government, which owns the cathedral, had pledged around $50 million over the next decade, leaving a bill of $135 million. To cover the rest, Picaud helped launch the Friends of Notre-Dame of Paris Foundation. It worked to find private donors both in France and across the Atlantic.
"We know Americans are wealthy, so we go where we think we can find money to help restore the cathedral," Picaud said in 2018. "Notre Dame of Paris isn't a Paris monument or French monument or a European monument but it's really a worldwide monument."
Notre Dame, one of the world's most visited landmarks, was constructed in 1163 during the reign of King Louis VII and was completed in 1345. The cathedral is a worldwide Parisian icon and site of some of Catholicism's most important relics, including the crown of thorns said to have been worn by Jesus. Henry VI of England was crowned inside the cathedral in 1431 and Napoleon Bonaparte was crowned emperor of France inside the cathedral in 1804.
French and U.S. troops celebrated there after liberating Paris from Germany in World War II, and for generations of Americans it's been a top tourist destination.
Last week, religious statues set atop Notre Dame came down for the first time in over a century as part of the restoration.
A 105-yard-high crane lowered the copper statues representing the 12 apostles and four evangelists onto a truck, giving the public a ground-level look for the first time on Thursday. The 3-meter-tall statues were to be sent to southwestern France for work.
The monument last got a major makeover more than 150 years ago, inspired partly by Victor Hugo's description of its decaying state in "The Hunchback of Notre Dame."