(CNN) -- Ashes found in the stove of a Romanian home have become the focus of investigations into the theft of seven valuable paintings by artists including Picasso, Matisse and Monet -- amid fears they may have gone up in smoke.
Experts from Romania's National History Museum have been analyzing the ashes for traces of paint and other chemicals that would confirm whether the works stolen last year from a Dutch museum have been destroyed.
The ashes come from the stove of one of the people indicted in the case, Ernest Oberlander-Tarnoveanu, general director of Romania's National History Museum said Thursday.
"Works of art and paintings have been burned and there are traces of typical red, yellow and green pigments," he told CNN affiliate ProTV.
But it's not yet confirmed whether these traces are all that remains of the stolen artwork.
Six people have been charged by the Romanian public prosecutor's office in connection with the theft from the Kunsthal museum in the Dutch city of Rotterdam on the night of October 15 last year.
Three men, Radu Dogaru, Darie Eugen and Adrian Procop, are charged with robbery counts.
A woman, Olga Dogaru, is accused of complicity in the crime by transporting and hiding the stolen artwork, the prosecutor's office said.
Two other defendants are accused of helping the alleged thieves by trying to value or sell the paintings.
The paintings, in oil and watercolor, include Pablo Picasso's "Harlequin Head," Henri Matisse's "Reading Girl in White and Yellow," Claude Monet's Waterloo Bridge" and "Charing Cross Bridge," and "Woman with Eyes Closed" by Lucian Freud. Works by Gauguin and Meyer de Haan were also taken.
The loss resulting from the theft is estimated at €18 million, the prosecutor's office said.