by Diana Stancy Correll

Military investigators announced that the 2017 crash of U.S. Marine Corps KC-130T over a Mississippi soybean field was primarily caused by a propeller blade that sliced through the main body of the aircraft.

The crash, which killed 15 marines and one sailor, occurred during scheduled travel for pre-deployment training.

According to the Marine Corps, the investigation revealed that a propeller on the aircraft didn’t receive necessary maintenance during its scheduled overhaul at Warner Robins Air Logistics Complex in 2011. Undetected corrosion in the propeller blade ultimately became a larger crack, allowing the propeller blade to detach.

“The procedures that were in place in 2011, those procedures if properly done should have detected that corrosion in 2011,” Brig. Gen. John Kubinec, the current commander of Warner Robins Air Logistics Complex, told CBS News. “The corrosion should have been detected. Why it wasn’t, we don’t know.”

The records are destroyed every two years, posing difficulties for identifying who should be held accountable for the accident. But the Marine Corps said it has worked with the Air Force to “identify new maintenance practices to mitigate risks and increase safety across the KC-130T fleet.”

“We remain devoted to supporting the families of the fallen and offer our sincere gratitude to the dedicated men and women who provided support from various federal, state and local agencies,” the Marine Corps said in a statement. “Their tireless efforts directly assisted in the response and investigation of this tragedy.”