Korea has found a serial number marked on fragments of torpedo propeller collected from the scene where the petrol ship Chonan of the navy sank in March, Yonhap News reported Wednesday.
The number was written in a font used in North Korea, and investigators have concluded that the 1,200-ton corvette came under a North Korean torpedo attack near the West Sea border on March 26 before breaking in half and sinking, Yonhap quoted officials in Seoul said.
Foreign experts from the United States, Britain and Australia working as part of an international team have also agreed to the assessment that a torpedo attack sank the Cheonan, officials said.
The defense ministry, however, denied a media report that a Korean word was also written on the propeller pieces.
South Korea plans to officially announce the investigation's outcome on Thursday. The announcement is expected to include the result of a computer simulation that a heavy, acoustic homing torpedo with a warhead weighing about 250 kilograms struck the Cheonan.
Investigators have also found that traces of explosives found in the Cheonan's wreckage were identical in composition to propellant explosives contained in a stray North Korean torpedo that South Korea recovered from the southern coast seven years ago.
It has been no secret that South Korean officials believe the North is responsible for the disaster that killed 46 sailors, though they have refrained from openly blaming the North until the investigation is complete.
After an initial examination of the Cheonan's wreckage, investigators had said the vessel was most likely struck by an underwater "non-contact" explosion, possibly from a torpedo or a sea mine.
North Korea has denied any involvement.