Near-bamboo interconnects have been reported to have the worst electromigration reliability. Using 1-dimensional computer simulation, the mechanical stress evolution and failure resulting from electromigration in near-bamboo Al interconnects are investigated. We vary the length of (polygranular) cluster and the distance between via and cluster. At initial stage, stress evolves fast in cluster region and forms a nearly straight profile over a whole interconnect at steady state. Cluster positions do not affect stress profiles at steady-state. Interconnects fail at two different positions: via and cluster end. As the distance between via and cluster decreases and the cluster length increases, cluster ends are easier to be failed. Transition of failure sites is considered to be a reason for multi-modal failure distributions reported experimentally for narrow interconnects.