Two people have been arrested after being found in possession of the Dutch master's "Child with a Soap Bubble" painting, which was valued at 20 million francs at the time of the theft, the source said.
This equates to roughly €3.9 million ($5.4 million) today.
The artwork was stolen from a museum in the nearby city of Draguignan in July 1999. It portrays a teenage boy with long dark brown locks, wearing a golden necklace and holding a soap bubble.
According to French newspaper Liberation, the two men were caught while trying to sell the painting.