Several experiments were performed at the Gran Sasso Laboratory on an 0.8-cm-diam × 5-cm-long, hyperpure, high-temperature vacuum-annealed palladium rod used as a cathode for electrolytic infusion of D2O and 0.1 M LiOH with regular additions of gaseous CO2 at a current density of 60 mA/cm2. In the very low background radiation environment, several gamma bursts lasting up to 15 min were detected whose intensity, in terms of cold fusion, was > 10−20 fusion/(deuteron pair · s). Under normal background conditions, none of these burst signals would have been detected with statistical significance. The shape and intensity of these signals are quite similar to those detected previously.