The U.S. Navy submarine accident that killed one sailor and injured 24 others occurred when the vessel -- traveling at high speed -- hit an undersea mountain head-on, Pentagon officials said Monday.

Saturday's accident near Guam caused part of the sonar dome, which is part of the submarine's nose, to flood, officials said.

The commander of the USS San Francisco, Kevin Mooney, has not been relieved of duty while the investigation of the accident continues.

Mooney could be relieved of duty if officials determine there is enough evidence that the accident could have been averted.

The investigation will look at the sub's speed, its location and whether the undersea formation was on navigational charts, officials said.

The submarine was traveling in excess of 33 knots -- about 35 mph --when its nose hit the undersea formation head-on, officials said.

The nuclear submarine docked Monday at a U.S. naval base in Guam, a spokesman with the U.S. Pacific Fleet said.

The San Francisco was escorted to port by U.S. Navy and Coast Guard vessels, according to Lt. j.g. Adam Clampitt. The submarine suffered "some external damage," he said.

At 12 noon, January 8, Guam Time, the USS SAN FRANCISCO hits an unchartered undersea mountain while travelling at high speed about 500 ft below surface.

The boat's pressure-hull begins just about where the missing bit ends. That the crew managed to recover and surface the boat after a head-on prang at 500 ft and 33 knots is miraculous.

UPDATE : More details and first-person accounts over at AEBrain. Also, please see Op-Ed article for how to help the family of the crewman who died.

Although all but ignored by Mainstream Media, the saga of the San Francisco's ordeal is one of the great naval dramas of our time.