Iraqi security forces patrolling near the Iranian border found six donkeys carrying dozens of high-explosive anti-tank mines, the U.S. military said in a statement Thursday.
The military said two men fled the scene in the religiously-mixed Diyala province where the insurgency is active.
It was not clear from the statement where the donkeys, a common form of transport in the region, had come from.
U.S. officials have often accused Iran of arming militant groups in Iraq.
The statement said Iraqi forces seized 53 Russian- and Italian-made anti-tank landmines and one anti-tank projectile.
"The donkeys were later released unharmed into the local area," the military said.