Heitz said investigators would interview workers from five companies working on the restoration.
France's deputy interior minister Laurent Nunez said saving the cathedral came down to a key timeframe of between 15 and 30 minutes, praising the work of firefighters who contained the blaze.
Huge sums have been pledged to fix the beloved Paris landmark, which President Emmanuel Macron has set a target of five years to finish.
While France mourned and President Emmanuel Macron vowed to rebuild all that was lost to the flames, newspapers told the story of the inferno through an array of striking images and headlines.
Almost $1 billion has already poured in from ordinary worshippers and high-powered magnates around the world to restore the fire-ravaged Notre Dame Cathedral in Paris, after the French president set a controversial five-year deadline to get the work done.
'All the 18th century steles, the pietas, frescoes, chapels and the big organ are fine'.
The three large stained-glass rose windows, among the most famous parts of the cathedral, were not destroyed, but might have been damaged by the heat and will be assessed by an expert.
Hours after President Macron - whose government had previously refused to spend more than a few million euros repairing the 855-year-old cathedral - launched an appeal for funds while it was still ablaze, nearly €700 million had been raised.
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Winnipeg historian Philippe Mailhot, who witnessed the fire at the St. Boniface Cathedral on July 22, 1968 when he was 13, finds the similarities between the two blazes striking.
Likewise, the centuries-old timber within the building's internal structure, much of which was crafted into an intricate support structure by medieval artisans, may be irreplaceable. "The same thing that we're told happened in Paris at Notre Dame as well", said Hutsko. They're the beams that caught fire and then brought the lead roof down with them.
"It's always exciting to give people back more than they ever expected", he said. "But perhaps it can't be recreated as it was". "Notre Drame" (Our Drama) said the headline on the front of the French newspaper Libération, alongside a photo of the moment the cathedral's spire collapsed.
"The cathedral ruins are still one of the more popular tourist destinations an Winnipeg and Manitoba".
French football club Toulouse will have the image of the Notre Dame cathedral on their shirts for their Champions Cup semi-final against Leinster this weekend, the president announced.
"It's a very deep sadness".
"We need to remind people of how France, and Europe, have recovered from other tragedies-the rebuilding after the World Wars for example", Maude said.
According to the Daily Record, she said: "When I looked at this photo last night, I was really astounded by what I saw".