Military investigators have concluded that a "friendly fire" incident in Afghanistan that killed one Afghan and five U.S. soldiers in June was caused by a series of avoidable miscommunications among air and ground forces.

A Central Command investigation report released Thursday said there was a collective failure to execute the fundamentals of the mission. As a result, two bombs dropped by an Air Force B-1 bomber stuck friendly forces; the five Americans and one Afghan killed were mistaken for enemy forces.

The five Americans killed were Staff Sgt. Jason A. McDonald, 28, of Butler, Georgia; Staff Sgt. Scott R. Studenmund, 24, of Pasadena, California; Spc. Justin R. Helton, 25, of Beaver, Ohio; Cpl. Justin R. Clouse, 22, of Sprague, Washington, and Pvt. Aaron S. Toppen, 19, of Mokena, Illinois.