Employee unloading 50-lb bags of ANFO. After unloading 3-4 bags, employee felt a ""pop"" in EE's shoulder then unloaded the rest of the bags (47). Reported to supervisor 30 min later. Orthopedic evaluation and X-ray next day confirmed nothing broken or dislocated. Employee given restriction, no pushing/pulling/lifting greater than 5 lbs with left arm. Follow up after MRI.