Network Neutrality states that all traffic in the Internet must be treated equally and thus cannot suffer unfair traffic differentiation (TD). Several solutions for detecting the presence of TD in the Internet have been proposed. However, locating where in the network TD is happening is still an open problem. In this work, we propose a strategy to locate Autonomous Systems (ASes) that are differentiating traffic. The proposed strategy takes advantage of AS-level routing properties to identify valid AS-level paths between end-hosts. It is then possible to select measurement points between which the AS-level paths traverse suspect ASes. Probes are sent from the measurement points and processed using end-to-end TD detectors based on statistical inference. The main idea is to check suspect ASes until only the AS that is actually discriminating traffic is filtered out. We first present results of experiments executed to validate the routing properties employed. Then the efficiency of the proposal for locating TD is evaluated using simulation. The results show that the proposed strategy is effective and efficient.