Four airmen killed in a plane crash while battling a fire in South Dakota will be remembered in a memorial service Tuesday.

According to U.S. Northern Command, the four killed were aboard a C-130 equipped with a MAFFS system. Two additional members of the crew survived the crash.

The plane went down around 6 p.m. near Edgemont, South Dakota. Prior to the crash, the crew had been supporting firefighting missions in the state, specifically the White Draw fire.

The dead are Lt. Col. Paul K. Mikeal, Maj. Joseph M. McCormick, Maj. Ryan S. David and Senior Master Sgt. Robert S. Cannon. All were from North Carolina, where the memorial service will be held.

The cause of the crash is not known and the incident is under investigation.

The plane belonged to the North Carolina Air National Guard's 145th Airlift Wing based at Charlotte-Douglas International Airport. U.S. Northern Command reports there were casualties including both injuries and deaths. Additional details were not provided.

According to a news release from the 302nd Airlift Wing out of Peterson Air Force Base, the C-130s from the Wyoming Air National Guard's 153rd Airlift Wing and the North Carolina National Guard's 145th Airlift Wing were moved to Cheyenne to fight fires in the northern states.

According to the same news release, the four aircraft from the California Air National Guard's 146th Airlift Wing, and the U.S. Air Force Reserve Command's 302nd Airlift Wing, will continue to operate from Peterson Air Force Base.

MAFFS equipped C-130's have been fighting the Waldo Canyon fire since June 25, two days after the fire started.

Operations of the other MAFFS equipped C-130's were suspended Monday. The fleet will spend the day to get the MAFFS crews together to “reflect, reset and review,” said Col. Jerry Champlin, 153rd Air Expeditionary Group commander.