A volunteer church assistant confessed to starting the July 18 fire that severely damaged a gothic cathedral in Nantes, western France, on Sunday.
The accused, a 39-year-old man of Rwandan descent, has been rearrested and charged.
An arson inquiry -- which typically carries a 10-year jail term -- was initiated last week after finding that the fire broke out in three different places in the Saint-Pierre-et-Saint-Paul Cathedral, which the volunteer had locked up the night before.
He was detained for questioning but released the next day without charge.
While the early morning fire was contained by 104 firefighters who managed to save its main structure, the church's priceless organ dating from the 17th century was completely destroyed.
The adjoining wooden choir stalls were also heavily damaged, and many original stained glass windows shattered beyond repair.
The cathedral had been partly destroyed in 1944 during World War II. A fire also broke out in 1972 which consumed the ancient roof. It was then rebuilt with concrete reinforcements.
The motivation for the crime is not known yet; however, according to Radio France International, the man had been facing an order to leave the country. He was living in France since 2012.
"My client cooperated. He bitterly regrets his actions and confession has been a relief for him," Quentin Chabert, the man's attorney, told the local Presse Ocean newspaper. "He is consumed by remorse and is overwhelmed by the magnitude of the events."
The government says it will ensure the cathedral's restoration.
The blaze came 15 months after a devastating fire at the Notre Dame Cathedral in the capital Paris.
