Allied troops have destroyed about 80 Iraqi mines in the Persian Gulf of the type that tore a gaping hole Monday in the hull of the Tripoli, an amphibious assault ship, Pentagon officials said.

But officials conceded Tuesday the Navy had failed to relocate and destroy at least 80 mines detected by location devices that continue to pose a threat to allied ships."By the time they can get a mine sweeper to it, the mine is gone," one official said. He added that many of the smaller mines that explode upon contact become untethered or are dropped by aircraft and move with the gulf current.

Just 11.5 miles from the 18,500-ton Tripoli, the impact of a warhead from an "influence" mine, laying on or near the bottom of the gulf, was set off by the close proximity of the 2-year old Princeton, a guided missile crusier that was screening for mines.