No cause has been determined for the ship's sinking, although the Yonhap News Agency quoted military officials as saying that an unidentified explosion tore a hole in the ship's rear, shutting off the engine.
South Korea's defense minister said it is possible an old mine could be behind the explosion.
Defense Minister Kim Tae-young told a parliamentary defense committee Monday that a North Korean sea mine from the 1950-53 Korean War could have caused the blast.
"It is possible that a North Korean sea mine could have drifted into our area," Kim said, according to Yonhap. He said North Korea brought in about 4,000 sea mines from the Soviet Union during the war and placed about 3,000 of them in the Yellow and East seas.
