The submarine collided with the amphibious transport ship USS Ogden Sunday off the coast of Oman as the ships were preparing to transfer two sailors, Pentagon officials said Monday.
A rear fuel tank of the transport was punctured while some damage occurred to the rear portion of the sub.
"Both ships continue to operate safely," said Pentagon spokeswoman Victoria Clarke. No one was injured.
The vessels were operating in support of the war in Afghanistan, Clarke said. The submarine was to continue on its planned journey to the island of Diego Garcia and will receive an underwater assessment of its damage there, Clarke said.
"What went wrong, we don't know," Rear Adm. John Stufflebeem, deputy director of operations for the Joint Staff, told reporters at the Pentagon briefing.
The Greeneville collided with a Japanese fishing vessel off Hawaii on Feb. 9, 2001, killing nine men and teen-age boys on the fishing boat. In August, the sub went aground while trying to enter the Saipan seaport in rough seas. It was the sub's first major deployment after undergoing repairs following the accident with the Ehime Maru.
Initial reports from the scene of Sunday's accident said the Greeneville was on the surface about 40 miles off the coast of Oman in the Northern Arabian Sea.
Stufflebeem said it appeared the rear portions of both ships touched, but it was unclear why. The admiral noted that normally the commanders of both ships have worked out the detailed maneuvers involved in transferring sailors from one ship to another well in advance.
The sailors from the Greeneville were being taken off the sub because of deaths in their families. They had been granted emergency leaves, Stufflebeem said.
However, the transfer was not completed due to the accident.
The Ogden is part of the amphibious ready group led by the USS Bonhomme Richard. Such transport ships act as supply ships and house Marines who are part of the three-ship group. Helicopters can land on their decks and transport sailors to shore.
In at-sea transfers, the ships remain several hundred feet apart and a small boat is launched from the dock transport. It maneuvers to the sub and then picks sailors up, Stufflebeem said.
The admiral said the Ogden would remain stationed in the Northern Arabian Sea and may be repaired at sea. Divers are assessing the damage, he said.
The submarine remained on the surface while traveling to Diego Garcia "as a precaution," the admiral said.
The weather in the area was described as windy at the time of the incident.
The collision tore a 5-inch-by-18-inch puncture in one of the Ogden's fuel tanks 15 feet below the water line on its right side. Several thousand gallons of light diesel fuel leaked into the sea, said a Navy officer, who commented only on condtion of anonymity.
Because of windy conditions, the fuel headed away from shore and toward the open sea, the officer said.
The sub's rear stern plane was damaged. That is part of the submarine that acts as a wing to control the angle of the ship's movement.
Clarke identified the commanders of the vessels as Cmdr. Lindsay Henkins of the Greeneville and Cmdr. William Edwards of the Ogden.
An investigation of the incident is under way, the Navy officer said.
By Susanne M. Schafer
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