The existence of cosmic rays with energies exceeding the Greisen-Zatsepin-Kuzmin cutoff is yet an unresolved puzzle. Even though the quality and quantity of experimental data on the Ultra High Energy Cosmic Rays (UHECR) has improved considerably , it has not been possible to explain the origin of UHECR. In this context it is of interest to simulate the development of electromagnetic cascades, initiated during the propagation of UHECR in the Cosmic Microwave Background (CMB). A new simulation code has been developed to study properties of electromagnetic cascades, generated in interactions with the background radiation fields. The detailed simulation of the relevant processes (pair production and Compton scattering) allows for a determination the energy spectra and arrival directions of secondary particles for different settings of background radiation, distances to the source and injection spectra. In this paper, first results obtained by simulating different injection spectra of photons are presented. The effect of cascading on the shape of the injected spectra is shown.