A photograph of a man and child playing in front of Notre Dame an hour before the cathedral caught fire on Monday evening has inspired a search online for the subjects.
Tourist Brooke Windsor took a photo of the pair appearing to dance in the square that fronts the landmark at around 5.57pm local time.
She has since appealed to Twitter users to share her image in an effort to track the man down and send him a copy.
Posting the photo, Windsor said: “I took this photo as we were leaving Notre Dame about an hour before it caught on fire. I almost went up to the dad and asked if he wanted it. Now I wish I had.”
The post generated more than 100,000 retweets and was translated into French by another user.
Windsor said the man may not be the child’s father, but could be “an uncle, brother, friend, who knows”.
She wrote: “I have not been able to find the folks in the photo but I am hopeful. Twitter sure knows how to step up.”
Just under 400 firefighters tackled the blaze for more than 12 hours throughout the night, but were unable to save the roof or the spire, which collapsed in dramatic fashion.
French President Emmanuel Macron said the cathedral would be restored: “We will appeal to the greatest talents and we will rebuild Notre Dame because that’s what the French are waiting for, because that’s what our history deserves, because it’s our deepest destiny.”
French billionaire Francois-Henri Pinault has pledged to donate 100 million euro (£86 million) to the rebuilding fund, with fashion billionaire Bernard Arnault donating a further 200 million euro (£173 million).