Didier Beauland, a pharmacist who has a shop near the basilica told The Local that those in the area saying workmen had been carrying out work in the roof of the church.
Fire chiefs later said that the blaze was “probably linked to waterproofing work that was taking place on the roof”.
“Firefighters arrived quickly but they had trouble getting to the basilica because the road was blocked as a crane was being dismantled,” said Beauland. “But eventually they got through.”
“As soon as it started the fire spread rapidly through the roof. It all happened so quickly,” he said.
“It’s very sad. Not good at all. It's a historic church. This is a Christian neighbourhood and who knows how long it will remain closed for now.”
The church was constructed between 1872 and 1889, and is one of two in the city of Nantes.
A #Nantes, violent incendie en ce moment à l'église Saint Donatien. pic.twitter.com/knOZNPGMFx
— Radio Côte d'Amour (@RadioCotedAmour) June 15, 2015
Terribles images #incendie #Nantes Basilique St Donatien. Solidarité aux nantais et soutien aux secours @SDIS44 pic.twitter.com/7y2YoWidgS
— Christophe Clergeau (@clergeau) June 15, 2015
Horrible !!! L'église saint Donatien en flamme ! #nantes #incendie pic.twitter.com/v8ynxxxpca
— Elodie Stella (@littlenantaise) June 15, 2015
L'église Saint Donatien en feu ! #Nantes pic.twitter.com/oZX3SD5uuB
— Maxime CLAVAL (@MaximeClaval) June 15, 2015
Incendie à la basilique Saint Donatien #nantes https://t.co/wAlTUzTROI
— Maxime CLAVAL (@MaximeClaval) June 15, 2015
En photo, #incendie #Nantes pic.twitter.com/APvQgFhlk5
— Maxime CLAVAL (@MaximeClaval) June 15, 2015