The fire began early Sunday outside the village of Orgon, Radio France Internationale reported.
The teenager, whose name was not reported, was being interrogated, prosecutor Christian Pasta said.
Several hundred firefighters battled the flames Monday, officials said.
"The blaze is under control but still active," said Hugues Parant, a senior government official in the region.
Gal Gadot cast as Wonder Woman for 'Batman vs. Superman'
Beyonce flaunts bikini body, Blue Ivy in vacation pics