We study the origin of the low temperature contribution to delayed recombination decay in scintillating materials. This contribution represents the loss of fast scintillation light even at the lowest temperatures. The possible role of quantum effects, as previously suggested, is tested both experimentally and theoretically. The experiments were performed on Lu2Si2O7:Pr3+ crystals. The results suggest that quantum tunneling between the luminescence center and a nearby defect is a good candidate for explaining the observed phenomena. (C) 2013 Elsevier B. V. All rights reserved.