The Marine Corps never publicly announced the high-casualty mishap, despite the fact that it came just weeks after a member of the same unit was paralyzed during a live-fire exercise.
The incident was confirmed to Military.com by 1st Lt. Cameron Edinburgh, a spokesman with 1st Marine Division.
"[Twenty-nine] of the Marines were cleared and released from the hospital the same day while one stayed overnight and was released the following day," Edinburgh said.
The injured Marines were members of the New York-based Charlie Company, 1st Battalion, 25th Marines, according to several sources familiar with events.
At least one of the injured was airlifted out of Twentynine Palms over concerns of serious injuries following the crash, one source said. All spoke to Military.com on the condition of anonymity, because they weren't authorized to discuss the accident, for which the investigation remains ongoing.
"We were really worried that some of our friends might've died," one Marine said. "The front ends of the 7-tons were just completely destroyed."
This was the second major mishap in 19 days for the Reserve infantry company, which was training at Twentynine Palms in preparation for an upcoming deployment to the Asia-Pacific region. On July 28, a lance corporal with the unit was paralyzed from the neck down after he was shot during a live-fire event.
That incident also was not disclosed by the Marine Corps, and didn't become public until it appeared weeks later in a report from the Naval Safety Center, which tracks major accidents, injuries and mishaps.
They also declined to address questions about whether the infantry company was cleared to deploy after the two accidents during their workup.
"No additional information is available at this time," Edinburgh said.