Seven Marines killed in explosion at Nevada training site

Seven U.S. Marines have been killed and at least seven more were injured in an explosion at a military ammunition storage facility in western Nevada.

The explosion happened late Monday during a training exercise at the Hawthorne Army Depot, about 135 miles south of Reno, reports Reuters.

Nine injured Marines were airlifted to Renown Regional Medical Center. Of those nine, one died, three are in serious condition and five are in fair condition, a hospital spokesperson told The New York Times. The identities of the dead will not be released until after their families are notified.

The exact cause of the blast is under investigation, but the Associated Press reports a source who says that it happened when a "60mm mortar exploded unexpectedly." The Marines issued a moratorium on firing such weapons worldwide until the investigation is complete, says the report.

Lt. Col. Craig Short, Hawthorne’s deputy commander, said a traffic collision was related to the explosion, reports CNN.