The crew of the USS Fitzgerald was likely at fault in the U.S. warship's collision with a cargo ship in June and had not been paying attention to their surroundings, according to the initial findings of an investigation, a U.S. defense official said.

Multiple U.S. and Japanese investigations are under way into how the Fitzgerald, a guided-missile destroyer, and the much larger ACX Crystal container ship, chartered by a Japanese company, collided in clear weather south of Tokyo Bay in the early hours of June 17.

The collision tore a gash below the Fitzgerald's waterline, killing seven sailors in what was the greatest loss of life on a U.S. Navy vessel since the USS Cole was bombed in Yemen's Aden harbor in 2000.