<p>WASHINGTON (AP) - U.S. officials said Monday they are concerned that other sarin-filled munitions may still exist in Iraq - and may not be well-marked - after evidence indicated a roadside shell that exploded contained the nerve agent.</p>
<p>No one was injured in the initial detonation Saturday, although U.S. soldiers who later transported the round did experience symptoms consistent with low-level nerve agent exposure, said a U.S. official speaking on the condition of anonymity.</p>