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 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.
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 that authorities remain "prudent" but are "much more optimistic" than earlier.
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.
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 they have ruled out arson, including possible terror-related motives for starting the blaze.
Prosecutors say Paris police will conduct an investigation into "involuntary destruction caused by fire."