The agency has been reviewing information found inside the Pakistani compound since the night raid and killing of bin Laden earlier in the week. Officials say what they have discovered since storming the hideout indicates one tactic might have been to somehow tip a train off its tracks. However, no concrete plans for such an attack have been found.
Meanwhile, relations between the US and Pakistan are still under strain, with attitudes towards America hardening in the wake of operation by the Navy Seals. Pakistan's army is threatening to reconsider its anti-terror cooperation with Washington if another similar assault takes place, which Islamabad says violated its sovereignty.