Nairobi -  An American reconnaissance plane crashed 6 miles (10 kilometers) from the only U.S. base in Africa, killing four service members on board, after returning from a mission in support of the war in Afghanistan, the military said Monday.

The statement said that the crash occurred at about 8 p.m. Saturday in Djibouti. U.S. personnel from Camp Lemonnier in the tiny Horn of Africa nation responded to the scene.

Specialist Ryan Whitney of the 1st Special Operations Wing said that initial indications are that the plane did not crash because of hostile fire. The plane was conducting an intelligence, surveillance and reconnaissance mission, he said. A statement from U.S. Africa Command called it a "routine" flight.

Amy Oliver, public affairs director of the Air Force 1st Special Operations Wing, said the single-engine, fixed-wing U-28A was returning from a mission in support of the Afghanistan war.

The cause of the crash is under investigation. Camp Lemonnier lies only miles from the border with Somalia.

The four killed in the crash included: Capt. Ryan P. Hall, 30, of Colorado Springs, Colorado, with the 319th Special Operations Squadron; Capt. Nicholas S. Whitlock, 29, of Newnan, Georgia, with the 34th Special Operations Squadron; 1st Lt. Justin J. Wilkens, 26, of Bend, Oregon, with the 34th Special Operations Squadron; and Senior Airman Julian S. Scholten, 26, of Upper Marlboro, Maryland, with the 25th Intelligence Squadron.