The Department of Defense reports that seven U.S. Marines were killed at the Hawthorne Army Depot in Nevada late Monday. Several others were injured in the fatal incident that occurred during a Live Fire Training exercise.

According to reports, a 60-millimeter mortar exploded as preparations to fire it were being conducted during a live-fire training exercise just prior to 10pm their time. The incident is currently under investigation, and the names of the victims of the tragic event will not be released for 24 hours after next of kin are informed.

The dead and injured in the explosion were from the 2nd Marine Division based out of North carolina.

The injured were taken to area hospitals in Reno, 140 miles to the northwest of the remote depot. There, they went through evaluations and treatment for their injuries.

“We send our prayers and condolences to the families of Marines involved in this tragic incident,” said Marine Corps Maj. Gen. Raymond C. Fox, 2nd Marine Expeditionary Force commanding general. “We remain focused on ensuring that they are supported through this difficult time. We mourn their loss, and it is with heavy hearts we remember their courage and sacrifice.”

Hawthorne was originally created as a Naval ammunition depot in 1930, but was transferred to the Army in 1977. The depot, then a plant, with its over 2,400 bunkers, was used for production of munitions until 1994.

Now the depot, sprawling over 226 square miles, is used for ammunition and explosives storage as well as a training facility for special forces preparing for deployment to other theatres with a similar desert-like terrain.