The paintings, valued at more than $23 million, were burned in a stove in the eastern village of Carcaliu by the mother of one of the thieves, Romanian Insider reported Wednesday.
Radu Dogaru, one of the men who broke into the Kunsthal museum in Rotterdam, brought the paintings to Romania inside pillows and deposited them at his mother's house.
The thieves were unable to sell the paintings and Dogaru's mother panicked after investigators searched her house in February.
She took the paintings by Picasso, Monet, Freud, Matisse, Gauguin and Meyer de Haan and burned them to help her son and keep from going to jail herself, authorities said.
Ashes from the paintings have been sent to Romania's National Museum of History for a technical analysis.
Police said Dogaru's mother faces 10 to 20 years in jail. In addition to her son, police have arrested Romanians Adrian Procop and Eugen Darie.
The destroyed works are identified as Picasso's "Tete d'Arlequin"; "Waterloo Bridge" and "Charing Cross Bridge" by Monet; Freud's "Woman with Eyes Closed"; Matisse's "La Liseuse en Blanc et Jaune"; Gauguin's "Femme Devant une Fenetre Ouverte," and Meyer de Haan's "Autoportrait."