South Korean investigators have all but ruled out an on-board accident or collision with rocks as the cause of a navy ship's sinking. The government is still treating the matter delicately, as suspicions remain that North Korea was involved in the sinking.
A multinational investigative team said Friday that the South Korean naval corvette, the Cheonan, split in half and sank earlier this month due to force applied from outside the ship.
Yoon Duk-yong, chief of the team, which includes marine salvage experts from the United States and Australia, says there is a far higher possibility of external explosion than one inside the ship.
The Cheonan sank as it patrolled waters west of the Korean peninsula, where North Korea disputes a United Nations-mandated maritime border. The two Koreas have fought three naval skirmishes there since 1999.
Salvage teams have managed to raise the biggest sections of the ship, and recover most of the bodies of the 46 sailors killed in the incident.
Yoon says fragments of the hull are bent inward, showing that the explosive force came from the outside. He adds the likeliest possible causes of an onboard accident have been eliminated.
He says there is no damage to the ship's ammunition depot, fuel tanks, or diesel engine room. Plastic coverings of electrical wires were also undamaged. Yoon says a lack of damage to the underside of the ship sharply reduces the chances it hit a reef or other underwater obstacle.
South Korean Defense Minister Kim Tae-yoon is among those who have publicly speculated the Cheonan may have been destroyed by a North Korean mine or torpedo. Officials in Seoul are carefully avoiding any direct accusations, but Kim says the matter is being treated seriously.
He says South Korea's government and military are treating the Cheonan incident as a "grave national security issue."
Investigators say it could take months or even years to find hard evidence of a North Korean role in the sinking, in the form of mine or torpedo splinters in the wreckage. They caution against drawing premature conclusions.
U.S. State Department Spokesman Philip Crowley said Thursday that Washington is offering full assistance to South Korea in the probe. He warned that North Korea's behavior in the region may affect multinational talks aimed at ending the North's nuclear weapons programs in exchange for energy, financial and diplomatic incentives.