U.S. Navy Rear Adm. John Kirby said the weapons were similar to what the U.S. had dropped, and it was possible ISIS had intercepted one of the drops.
"We are very confident that the vast majority of the bundles did end up in the right hands," he said. "In fact, we're only aware of one bundle that did not."
The Wall Street Journal reported the parachute of the GPS-guided package malfunctioned during the drop, causing it to drift from its target.
The accidental drop of the weapons cache prompted thank-yous from ISIS supporters on Twitter. The loss was more of an embarrassment than a strategic problem for the U.S., the AP reported. ISIS already controls millions of dollars worth of weapons left behind by fleeing Iraqi soldiers.