Stove ashes probed for traces of stolen Picasso, Monet works By Saskya Vandoorne, Laura Smith-Spark and Liliana Ciobanu, CNN Experts analyze ashes found in a stove to see if they are the remains of stolen artwork Works by Matisse, Picasso and Monet were among paintings taken from a Dutch museum Six people have been charged in Romania in connection with the theft last year There are traces of pigments in the ashes from the stove of one of those charged, official says (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. Notorious art heists The search for stolen masterpieces "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. July 19, 2013 -- Updated 1852 GMT (0252 HKT) July 18, 2013 -- Updated 2035 GMT (0435 HKT) Russian opposition leader Alexei Navalny is free to appeal a jail sentence for embezzlement. But who is this critic of President Putin?