In this Thursday, May 2, 2013 file photo, Philippe Lefebvre, 64, plays the organ at Notre Dame cathedral in Paris. (AP Photo/Christophe Ena)
File photo: A crown of thorns believed to have been worn by Jesus Christ and bought by King Louis IX in 1239 at Notre Dame Cathedral, Paris. (AP Photo/Remy de la Mauviniere)
This handout photo taken by Evgeny Feldman shows people holding candles inside Notre-Dame-cathedral in Paris. (Evgeny Feldman via AP)
This photo tweeted by Paris mayor Anne Hidalgo shows artifacts saved from the fire at Notre Dame cathedral. (Twitter via AP)
A man is pictured near charred glass windows Notre Dame cathedral in Paris. (AP Photo/Francois Mori)
A man is pictured near charred glass windows Notre Dame cathedral in Paris. (AP Photo/Francois Mori)
People make pictures of Notre Dame cathedral Tuesday April 16, 2019 in Paris. (AP Photo/Michel Euler)
Firefighters declared success in a more than 12-hour battle to extinguish an inferno engulfing Paris' iconic Notre Dame cathedral. (Christophe Petit Tesson, Pool via AP)
The glass windows are pictured inside the damaged Notre Dame cathedral in Paris, Tuesday, April 16, 2019. (Christophe Petit Tesson, Pool via AP)
Holes seen in the dome inside the damaged Notre Dame cathedral in Paris, Tuesday, April 16, 2019. (Christophe Petit Tesson, Pool via AP)
Photo issued Wednesday April 17, 2019 by the Paris City Hall, showing artefacts rescued from the Notre Dame blaze in Paris. (Henri Garat/Ville de Paris via AP)
Photo issued Wednesday April 17, 2019 by the Paris City Hall, showing artefacts rescued from the Notre Dame blaze in Paris. (Henri Garat/Ville de Paris via AP)
Photo issued Wednesday April 17, 2019 by the Paris City Hall, showing artefacts rescued from the Notre Dame blaze in Paris. (Henri Garat/Ville de Paris via AP)
Photo issued Wednesday April 17, 2019 by the Paris City Hall, showing artefacts rescued from the Notre Dame blaze in Paris. (Henri Garat/Ville de Paris via AP)