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.
Boston schools pull out free condoms over wrapping complaints
Ray Liotta sues skin care company over use of likeness