Civilian was at US sub controls

Nine people are still missing - 26 people survived

A civilian was at the helm position of the US military submarine that rammed and sank a Japanese trawler off Hawaii, a US defence official has confirmed.

But there is no indication the civilian played any role in the accident, said the official, speaking on condition of anonymity.

Nine survivors have returned to Japan

The US Navy, while continuing its search for the nine sailors missing from the trawler Ehime Maru, plans to send underwater robots to survey the seabed where the ship sank on Friday.

The USS Greeneville was conducting a drill in which the submarine dives to about 120 metres (400 feet) and then rapidly surfaces - known as an "emergency main ballast blow."

Normally the sub's commander would ensure that no objects were in the way but the Greeneville failed to detect the presence of the fishing vessel.

Pentagon spokesman Rear Admiral Craig Quigley said no details of the accident would be released until the Navy had completed its investigation. The US National Transportation Safety Board also is investigating.

'Routine visitors'

Navy spokesman Commander Greg Smith declined to comment on the incident but said civilians were routinely allowed aboard US submarines and that it would not be unusual for a civilian to be at one of the sub's three main control positions.

President Bush has apologized to Japan

"The civilian is not in control of any actions that were not ordered by the commanding officer," he said.

The position occupied by a civilian aboard the Greeneville would control the submarine's heading and angle, one official said.

The Navy has declined to release the identities of the 16 civilians reported to have been aboard the Greeneville.

Rear Admiral Quigley said the civilians, described by another official as local community and business leaders, had requested that the Navy not reveal their identities.

US President George W Bush said he apologized to the Japanese people in a telephone call to Prime Minister Yoshiro Mori.

"I apologized on behalf of our nation for the accident that took place and the lives that are missing," Mr Bush told reporters on Air Force One, while returning from a visit to Norfolk Naval Air Station in Virginia.

"He asked me to do everything I could, which we are doing, to locate the missing folks," he said. "I think we need to do what we need to do to get the bodies out of there, if they're there."

On Tuesday, tearful relatives of the missing visited the accident site, where they called out their loved ones' names and cast flowers into the sea. Nine students who were among the 26 people rescued from the Ehime Maru have returned to Japan.