(CNN) Rescuers are searching for crew members aboard two US Marine planes that collided mid-air off the coast of Japan in the early hours of Thursday morning, according to Japan's Ministry of Defense and the US Marine Corps.

At least one Marine was killed in the crash and the body has been recovered, the Marine Corps said in a statement. A second Marine was rescued and is described to be in fair condition. Five other Marines remain missing.

The KC-130 and F/A-18 collided at 1:42 a.m. local time, according to a Japanese Defense Ministry statement.

According to a statement from the US Marine Corps, the crash happened during an aerial refueling that was part of a routine training. The primary mission of a KC-130 is airborne refueling.

It is believed five crew were on board the KC-130 and two on the F/A-18 at the time of the crash, two US defense officials told CNN.

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