CAMP PENDLETON, Calif.–The leader of a Marine landing team was relieved of command Oct. 13 after an amphibious assault vehicle sank off the Southern California coast in July, killing nine people, the military announced Oct. 13.

Lt. Col. Michael J. Regner was relieved of command based on “a substantial amount of information and data,” according to a statement by Lt. Gen. Karsten S. Heckl, the commanding general of the I Marine Expeditionary Force. The statement did not provide more details.

Regner commanded the battalion landing team of the 1st Battalion, 4th Marine Regiment, 15th Marine Expeditionary Unit.

“Heckl relieved Regner due to a loss in trust and confidence in his ability to command” as a result of the July 30 accident, according to a Marine Corps statement.

The military is investigating what caused the tank-like amphibious vehicle to sink off San Clemente Island on July 30 after completing routine training. The troops were heading back to a Navy ship from the island, which lies about 70 miles west of San Diego.

The amphibious vehicle, with 16 people on board, rapidly sank in 385 feet of water.

Seven Marines were rescued.

Another Marine was pronounced dead at the scene. The bodies of seven Marines and a Navy hospital corpsman were later recovered by an underwater salvage team. Those who died ranged in age from 18 to 22.