Neutron Activation Analysis (NAA) is a powerful and sensitive technique for measuring trace amounts of impurities. In this work, we have applied NAA to the problem of identifying metallic impurities within the bulk of solar-grade cast multicrystalline silicon (mc-Si) wafers. In particular, the change in concentrations of these contaminants after phosphorus gettering is monitored, revealing a marked reduction in some metal species, but not in others.