U.S. Customs and Border Protection grounded its fleet of unmanned aircraft Tuesday after losing one worth $12 million in the Pacific Ocean.
The unarmed aircraft had a mechanical failure while on patrol of the southern California coast. The crew determined that it wouldn't make it back to Sierra Vista, Arizona, "and put the aircraft down in the water," the agency said in a statement.
It's unknown what caused the failure.
The majority of the aircraft is submerged. The Coast Guard is assisting in recovering any floating pieces, an official said.
Unmanned aircraft systems are technically not "drones," which operate under preprogrammed instructions, Customs and Border Protection says. They are piloted remotely.
Customs and Border Protection's fleet of 10 is now down to nine, all grounded, an agency official said. The one lost Tuesday cost about $12 million, plus another $6 million for the ground system.
The agency lost a smaller unmanned aircraft in 2006. It ultimately crashed about 200 yards from a home, the official said.
In November two sailors were treated for minor burns after a drone malfunctioned and crashed into a guided missile cruiser off the coast of Southern California.
The ship was testing a combat weapons system. The drone was being used to test the ship's radar tracking when it malfunctioned, veered out of control and struck the cruiser, the military said.