The main target of this study is a search for the origin of two ground level enhancements (GLEs), observed on December of 2003 at sea level by using the TUPI muon telescope. The results show that one of them has a strong correlation with solar flare, while the other has an unknown origin, because there is not satellite report of solar flare, nor the prompt X-ray emission and neither the excess of nuclei during the raster scan where the GLE was observed. Even so, two possibilities are analyzed: the solar flare hypothesis and the gamma ray burst (GRB) hypothesis.