Crew members aboard the USS Fitzgerald "should have spoken up" long before the American warship collided with a massive cargo vessel off the coast of Japan last month, U.S. officials said on Friday.

"There were many people who should have spoken up," one U.S. official, who was not authorized to speak publicly about an ongoing investigation, told Fox News.

The "rules of the road" at sea mandate states that any ship should keep out of the way of any ship on her right, or starboard, side.

The USS Fitzgerald was struck on her starboard side on June 17 by a cargo ship three times larger than the American warship. Seven American sailors were killed in the incident.

But the investigation into the collision still has a long way to go, a Navy official said Thursday.

"We are in the early stages of the investigation process to develop a comprehensive picture of what caused the collision and do not have any definitive information to release at this time," Rear Admiral Dawn Cutler, U.S. Navy Chief of Information, said in a statement. "It is premature to speculate on causation or any other issues. Once we have a detailed understanding of the facts and circumstances, we will share those findings with the Fitzgerald families, our Congressional oversight committees and the general public."

One U.S. official pointed to the U.S. Coast Guard's Navigation Rules & Regulations Handbook which clearly states this rule: "When two power-driven vessels are crossing so as to involve risk of collision, the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances of the case admit, avoid crossing ahead of the other vessel."

There are two navigation teams aboard every Navy warship, one on the bridge where the ship is driven and another team below the bridge in the combat information center, where a backup chart and radar team are located. This means there were two teams of sailors that missed recommending and taking "decisive and early action," the official told Fox News.