Soldiers operating south of Baghdad reported finding another dozen weapons caches in searches over the weekend, including one that contained an ominously large string of aircraft bombs.

Troops from the 4th Battalion, 31st Infantry Regiment, 10th Mountain Division have now reported finding 30 weapons caches of various sizes during the past week.

The unit is operating as part of Operation Commando Hunter, described as an effort to take away insurgents’ “sanctuary” in southern Baghdad, where a large-scale effort to end sectarian violence is ongoing.

The biggest find were four 500-pound aircraft bombs in one cache.

“The munitions are believed to have been intended for building a massive improvised explosive device to be used in Baghdad,” the U.S. military said in a statement.

No further information was available on Monday about where or how the device was to be used.

Military officials say aircraft bombs of various sizes have been modified and used to devastating effect as roadside bombs and in car bombs.

Other weapons found within the caches included “large numbers” of assault rifles, machine guns, ammunition and bomb-making materials.

More than 80 rockets, heavy mortar rounds and remote control triggering devices have also been found, officials said.

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