Firefighters douse flames from the burning Notre Dame Cathedral as people look on in Paris, France April 15, 2019. Distraught Parisians and stunned tourists gazed in disbelief on Monday as a monstrous inferno tore through Paris' Notre-Dame cathedral, one of the world's best-loved monuments. REUTERS/Benoit Tessier

Sparks fill the air as Paris Fire brigade members spray water to extinguish flames as the Notre Dame Cathedral burns in Paris, France, April 15, 2019. Thousands of onlookers lined bridges over the Seine and along the river's embankments, held at a distance by a police cordon as the blaze engulfed the cathedral's roof. REUTERS/Philippe Wojazer

Fire fighters douse flames of the burning Notre Dame Cathedral in Paris, France April 15, 2019. Distraught Parisians and stunned tourists gazed in disbelief on Monday as a monstrous inferno tore through Paris' Notre-Dame cathedral, one of the world's best-loved monuments. REUTERS/Benoit Tessier

Sparks fill the air as Paris Fire brigade members spray water to extinguish flames as the Notre Dame Cathedral burns in Paris, France, April 15, 2019. Thousands of onlookers lined bridges over the Seine and along the river's embankments, held at a distance by a police cordon as the blaze engulfed the cathedral's roof. REUTERS/Philippe Wojazer

Fire fighters douse flames of the burning Notre Dame Cathedral in Paris, France April 15, 2019. Distraught Parisians and stunned tourists gazed in disbelief on Monday as a monstrous inferno tore through Paris' Notre-Dame cathedral, one of the world's best-loved monuments. REUTERS/Benoit Tessier

People watch as fire fighters douse flames of the burning Notre Dame Cathedral in Paris, France April 15, 2019. Thousands of onlookers lined bridges over the Seine and along the river's embankments, held at a distance by a police cordon as the blaze engulfed the cathedral's roof. REUTERS/Benoit Tessier