PARIS -- French President Emmanuel Macron has promised to rebuild Notre Dame Cathedral and says he is seeking international help to restore the Paris landmark.
Macron said after the French capital's fire chief announced the emergency response had changed into a monitoring and mop-up operation, "The worst has been avoided although the battle is not yet totally won."
Macron said a national fundraising campaign to restore Notre Dame would be launched Tuesday and he called on the world's "greatest talents" to help.
The French leader credited the "courage" and "great professionalism" of firefighters with sparing Notre Dame's facade and two landmark towers from being destroyed.
The Paris prosecutors' office says investigators are treating the blaze that destroyed part of Notre Dame as an accident for now.
The prosecutors' office said late Monday they have ruled out arson in Monday's fire, including possible terror-related motives for starting the blaze.
Prosecutors say Paris police will conduct an investigation into "involuntary destruction caused by fire."
A French official and the Paris fire chief say they think Notre Dame Cathedral's landmark rectangular towers have been saved from the fire that caused horrific damage.
Junior Interior Minister Laurent Nunez said late Monday that authorities remain "prudent" but are "much more optimistic" than earlier in the night.
Paris fire commander Jean-Claude Gallet said a major accomplishment of hundreds of firefighters was stopping the flames from spreading to the north tower belfry.
Gallet says two-thirds of Notre Dame's roofing "has been ravaged." He says one firefighter was injured.
He says fire crews will keep working overnight to cool down the structure.
Hidalgo says the significant collection art work and holy objects kept inside the church has been recovered.
Parisians have gathered to say prayers and sing hymns In front of the nearby Saint Julien Les Pauvres church as the massive blaze at Notre Dame Cathedral burns only a few hundred meters away.
Flames and smoke rose in the sky behind the singers. A couple hundred people kneeling in prayer at the center of a larger group, who are standing around the edge and joining in the hymns between the prayers.
Paris archbishop Michel Aupetit is inviting priests across France to ring the bells of their churches in a call for prayers for Notre Dame.