A U.S. Navy nuclear-powered attack submarine, under heavy escort, has arrived back at its home port of Guam after a fatal accident at sea.
With military helicopters hovering above and a flotilla of escort ships alongside, the USS San Francisco returned to Guam on Monday. An enlisted man working in a machinery room died and 23 other sailors were injured when the vessel collided with some underwater object on Saturday.
The Navy says it does not know what the attack submarine hit while it was submerged in the eastern Marianas Basin, some 560 kilometers south of Guam. But Pacific Fleet spokesman Lt. David Benham says it was not likely another submarine.
"We have no data to suggest that there were any other vessels of any kind, submarine or otherwise, operating in the area at that time," said Mr. Benham. "Every indication is that it struck a geological feature."
The submarine, which was en route to a port call in Australia, surfaced in the Pacific Ocean after the accident and returned to Guam on its own power.
Military aircraft, a Navy submarine tender and a Coast Guard cutter were dispatched from Guam to transfer medical personnel onto the San Francisco to treat the injured and to escort the damaged vessel back to port. A spokesman says the injuries included broken bones and lacerations.
The Navy says the submarine's nuclear reactor was not damaged, there was no leak of radioactivity and the vessel's hull is intact.
Some Naval officers on Guam speculated Monday that the submarine ran into an undersea geological feature that had been shifted by the December 26 earthquake off Indonesia that triggered the lethal Asian tsunami. Lt. Benham says that theory is a long shot.
"The distance between the earthquake in the Indian Ocean and the location where submarine struck whatever it is that it struck is about the distance across Australia," he said. "It's a tremendous amount of distance so there's no indication that the two events are at all related."
The last major incident involving a U.S. Navy submarine occurred in 2001, when the USS Greenville rammed a fishing vessel as it surfaced off Hawaii, killing nine Japanese. The commander was later forced to retire.