DRAWSTRING OF A RE-TIED BAG HUNG ON A BELT MOTOR CAUSING THE BAG TO BECOME UNBALANCED. WHEN THE BAGGING CYCLE ENDED THE BAG RELEASED AND FELL TOWARD EMPLOYEE. HE STEPPED BACK AS THE BAG FELL ON HIS FEET.(APPROX 2000#)AS HE MOVED HE FELT PAIN IN LOWER BACK. RESTRICTED DUTY REQUIRED.