The crew of a US submarine that ran aground in the Pacific Ocean in January did not adequately review navigation charts, a Navy report says.
The submarine hit an underwater mountain
The grounding could have been avoided if the crew had observed "prudent navigation practices", it says.
A sailor died and several were injured in the accident 600km (350 miles) south of the island of Guam, one of the most important US Pacific bases.
The nuclear reactor on the USS San Francisco was not damaged.
Data not transferred
The vessel was on its way to Australia, when it ran aground and suffered severe external damage.
The submarine hit a mountain while submerged 157m (525 feet) below the ocean's surface.
The mountain did not appear on the chart being used for navigation.
But other charts displayed "a navigation hazard in the vicinity of the grounding", the US Navy's 124-page report said.
It blamed the team for not reviewing those charts adequately and for not transferring "pertinent data" to the chart being used for navigation.
"Even if not wholly avoided, however, the grounding would not have been as severe and loss of life may have been prevented," the report said.
The Los Angeles-class submarines are 109.73m (360 ft) long and are classed as attack vessels, designed to counter enemy submarines or surface vessels. They are equipped with a single nuclear reactor.