An altar table from the former Augustinian church in Fribourg (Switzerland) was studied by means of neutron and X-ray imaging to investigate the embedded reliquary. The neutron transmission images showed that the sepulcrum contained three objects showing high contrast and high attenuation. As the particles were almost invisible in the X-ray image, it was assumed that they were organic material. Comparative measurements on reference samples of materials possibly contained in such a reliquary (bone, teeth, leather, incense and parchment) suggest that the particles are bone fragments. Besides an assessment of the content, the results from the neutron investigation allowed a proposal of the probable geometry (i.e., shape and dimensions) of the sepulcrum.