A torpedo has been determined as the probable cause of the sinking of the Navy corvette Cheonan, according to a preliminary inspection of the split surface of the ship after it was salvaged from the West Sea. Defense Minister Kim Tae-young told reporters Sunday, "Basically, I think the bubble jet effect caused by a heavy torpedo is the most likely cause." Kim added the ongoing investigation is looking into other causes as well.
An investigation team reached a tentative conclusion on Sunday that the cause was a "non-contact external explosion" in the lower left hand section of the vessel resulting from either a torpedo or a mine.
"The possibility of an underwater non-contact explosion is bigger than that of an underwater contact explosion, considering the shape of the severed surfaces and conditions," chief investigator Yoon Duk-yong told reporters. The investigation team once again ruled out an internal explosion because no damage was done to the ammunition storage or the fuel tank, while the covering of the electrical wiring in the vessel remained in good condition and there were no signs of an internal fire. There are no scratches on the bottom of the ship, and the sonar dome is in good condition, making it improbable that the ship ran onto a reef. Also, the jagged and tattered surface of the split section led investigators to rule out metal fatigue.
A probe of both the stern and bow of the Cheonan by the investigators showed that a 3.2 m section of the lower left hand section of the vessel and a 9.9 m section of the starboard side were lost in the blast and the hull around the split section was bent upwards. This demonstrates that a blast occurred in the lower left hand section of the vessel and ripped through the upper right hand portion.