The transmitted light through random media is studied at nm with a Mach - Zehnder interferometer. The optical heterodyne detection used allows a coherent detection with a sensitivity corresponding to an optical thickness of 25. In addition to the standard exponential decrease for the transmitted light in accordance with the scattering cross section value computed from the Mie theory, we observed a distinct component for optical thicknesses above 15 and 17 for polystyrene beads with diameters of 0.94 and respectively. This second component, involving light scattered onto the detector, was hardly detected with smaller scatterers but is clearly present in tissue samples. A measurement of the angular distribution of the scattered light confirmed the coherent detection of non-ballistic light for particle suspensions and blood samples.