The Army Corps of Engineers is delaying the use of explosives to blast away treacherous rock pinnacles on the Mississippi River in southern Illinois because crews are having so much success removing the rocks with excavating machinery.

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The corps has hired contractors to use explosives to remove about six miles of rock pinnacles near Thebes, Ill. The river's water level is so low in the area between St. Louis and Cairo, Ill., that barge traffic is threatened. Blasting was scheduled to begin yesterday.