A method for detecting fraud in a Reverse Vending Machine System, the Reverse Vending Machine System having at least one radiation emitting device, a radiation detecting device and at least one processing unit, the method comprising the steps of: - receiving a food or beverage container, which carries a validation mark and a background around said validation mark, wherein said validation mark is a security mark and/or barcode, and said background is arranged in the vicinity of said validation mark, which validation mark is configured to be read by use of barcode decoding, and/or by use of character recognition and/or letter recognition and/or pattern recognition to decode a graphical message having a spatial extension; - illuminating the surface of said food or beverage container, which contains said validation mark, with radiation comprising wavelengths within the wavelength range of optical radiation, which radiation is emitted from said at least one radiation emitting device; - detecting radiation (306, 108) being emitted from said at least one radiation emitting device and subsequently reflected at said food or beverage container, and/or radiation being emitted from said at least one radiation emitting device and subsequently transmitted through said food or beverage container, and/or detecting radiation emitted from said food or beverage container in response to said illumination with said radiation detecting device; - transmitting information corresponding to the detected radiation from said radiation detecting device to said at least one processing unit; - at said at least one processing unit: - analyzing said information corresponding to the detected radiation to identify a validation area on said container, the validation area containing said validation mark and said background arranged in the vicinity of said validation mark, and determine the existence of additional radiation emitted from said background in the vicinity of said validation mark, which additional radiation is not received from valid food or beverage containers, and which additional radiation comprises fluorescent radiation, and - upon determination of the existence of said additional radiation classify said food or beverage container as fraudulent. - receiving a food or beverage container, which carries a validation mark and a background around said validation mark, wherein said validation mark is a security mark and/or barcode, and said background is arranged in the vicinity of said validation mark, which validation mark is configured to be read by use of barcode decoding, and/or by use of character recognition and/or letter recognition and/or pattern recognition to decode a graphical message having a spatial extension; - illuminating the surface of said food or beverage container, which contains said validation mark, with radiation comprising wavelengths within the wavelength range of optical radiation, which radiation is emitted from said at least one radiation emitting device; - detecting radiation (306, 108) being emitted from said at least one radiation emitting device and subsequently reflected at said food or beverage container, and/or radiation being emitted from said at least one radiation emitting device and subsequently transmitted through said food or beverage container, and/or detecting radiation emitted from said food or beverage container in response to said illumination with said radiation detecting device; - transmitting information corresponding to the detected radiation from said radiation detecting device to said at least one processing unit; - at said at least one processing unit: - analyzing said information corresponding to the detected radiation to identify a validation area on said container, the validation area containing said validation mark and said background arranged in the vicinity of said validation mark, and determine the existence of additional radiation emitted from said background in the vicinity of said validation mark, which additional radiation is not received from valid food or beverage containers, and which additional radiation comprises fluorescent radiation, and - upon determination of the existence of said additional radiation classify said food or beverage container as fraudulent.