<p>The Army is investigating whether pro-Saddam insurgents have a new mystery weapon that can disable the powerhouse M1AI Abrams tank - while leaving only a pencil-size hole in the hull. The Army Times reported yesterday that commanders in Iraq have grown alarmed about the prospect that exotic new weaponry may be in the hands of the death squads after one of the 69-ton workhorse tanks was disabled while on patrol in Baghdad Aug. 28.</p>