Last week's mix-up between Korean and U.S. militaries over a U.S. drone flight occurred due to a communication error at the working level, a Korean military official said Monday.

The incident came after Korean forces detected the U.S. spy drone flying over the inter-Korean border area Thursday, mistaking it for an enemy threat and almost preparing to shoot it down.

The unmanned flying vehicle was with a U.S. Marine Corps taking part in a routine combined exercise with the Korean Marines at a U.S. training site in Paju, north of Seoul.

The South's military conducted an inspection of the Army's 1st Corp, which has jurisdiction over the firing range.

"The inspection confirmed that the incident occurred due to a communication error between working-level personnel regarding on-site airspace control procedures," an official from the Joint Chiefs of Staff (JCS) told reporters.

"The command reporting system did not function properly, and it was also due to a customary practice of failing to comply with official flight authorization procedures," the official said.