At least 300 million euros ($339 million) have been pledged so far to help rebuild the Notre Dame Cathedral, which nearly burned to the ground on Monday.
French billionaire Bernard Arnault and his conglomerate LVMH have pledged 200 million euros, according to The Associated Press, and François-Henri Pinault, another French billionaire, said he and his family would donate 100 million euros, according to CNN.
Before the fire, an estimated investment of 150 million euros over three decades likely would've been required for restoration work on the massive church, a group called Friends of Notre Dame told ABC News. Authorities in Paris had been concerned about raising the funds. Total repair costs following the devastating fire aren't yet known.
Construction on Notre Dame began in 1163 and lasted about a century. It officially was completed in 1345.
An architecture professor at the University of Notre Dame in South Bend, Indiana, told ABC News it may take five to seven years for the cathedral just to recover from the blaze.
"The original building took over 100 years to actually come together, piece by piece," Krupali Krusche said in an interview. "It will be done. But a recent project in Europe of that scale has taken up to 10 years to produce."
Although largely famous for its ornate exterior stonework, most of the cathedral's interior was wood, which fed the flames like a "cooker," she added. But even masonry that survived the fire may be terribly damaged.
"Once a fire starts in the center or the heart of the building, it's pretty easy to, you know, completely take away the core of the building," Krusche explained. "And this situation was that of a cooker, basically, where you're getting the fire in the heart of the plate, and it starts growing and growing. The flames went very high yesterday ... and engulfed the whole heart of the of the church."
The fire, reported to be extinguished early Tuesday, was battled by some 500 firefighters.
"They are fighting with courage and determination. Your country thanks you," French President Emmanuel Macron said late Monday. The fire, he added, is a "terrible tragedy," and he vowed, "This cathedral ... we will rebuild it."
ABC News' David Rind and David Wright contributed to this report.
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