( CNN ) -- Ten days after grounding its fleet of drones , federal border officials Friday says they have determined the cause of a January 28 drone crash and are returning the remaining aircraft to the sky to continue patrolling U.S. borders . Officials say the generator on the aircraft -- a $ 12 million variant of the Predator B -- failed , forcing operators to ditch the plane in the Pacific Ocean . Customs and Border Protection spokesman Michael Friel said in a statement that procedures in place for this possibility `` were properly carried out by the flight crew . '' Mechanical steps have been taken to mitigate the vulnerability , he said . On January 28 , a flight crew ditched the unmanned aircraft in the ocean 20 miles southwest of San Diego after concluding they were unable to return it to its base in Sierra Vista , Arizona . With the loss of the aircraft , CBP now has nine unmanned aircraft . In 2006 , the agency lost another unmanned aircraft when it lost communications with it as it patrolled the southern border . In that instance , the aircraft was programmed to go to a pre-designated airspace and `` loiter '' in the event of a loss of communications . But it instead glided for 14 minutes , covering 30 miles , and crashed within a couple hundred yards of a rural home .
Customs has grounded aircraft after January 15 incident . Aircraft was grounded in the Pacific after its onboard generator failed , not found . Procedures were ` ` properly carried out by the flight crew , '' spokesman says .