Ferromagnetism in La-doped single crystal CaB6 is interesting because it has no partially filled d- or f- orbits in CaB6. In this paper, we have investigated the relationship between the ferromagnetic properties with the La content in CaB6 polycrystalline ceramics prepared by redox method. Contrary to the single crystal results, we found that there is no direct correlation with the level of La substitution in ceramics samples Ca1-xLaxB6 (0 £ x £ 0.03). Instead we have shown that it is related to Fe impurities. Our results show it is important to consider the magnetic impurities in discussing the weak ferromagnetism in borides.