NAIROBI, Kenya (AP) — An American reconnaissance plane crashed 6 miles 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. All four were assigned to units at Hurlburt Field, Ft. Walton, Fla., according to the Department of Defense.

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 are: Capt. Ryan P. Hall from the 319th Special Operations Squadron, Capt. Nicholas S. Whitlock and 1st Lt. Justin J. Wilkens from the 34th Special Operations Squadron and Senior Airman Julian S. Scholten from the 25th Intelligence Squadron

• Hall, 30, was a U-28A pilot on his seventh deployment. He entered the Air Force in 2004, receiving his commission through the Reserve Officer Training Corp at The Citadel. He had been assigned to the 319th SOS at Hurlburt Field since 2007 and had more than 1,300 combat flight hours.

• Whitlock, 29, was also a U-28A pilot and was on his fifth deployment. He entered the Air Force in 2006, receiving his commission through the Officer Training School. He had been assigned to the 319th SOS and then to the 34th SOS at Hurlburt Field since 2008 and had more than 800 combat flight hours.

• Wilkens, 26, was a combat systems officer on his third deployment. He entered the Air Force in 2009, receiving his commission through the Air Force Academy. He had been assigned to the 34th SOS at Hurlburt Field since April 2011 and had more than 400 combat hours.

• Scholten, 26, was a mission systems operator assigned to the 25th IS at Hurlburt Field since 2009. He enlisted in the Air Force in 2007. He had more than 600 combat hours in six different airframes and was on his third deployment.

Associated Press reporter Suzanne Gamboa in Washington contributed to this report.