South Korean investigators on Friday said an external explosion was the most likely cause of the mysterious sinking of a 1,200-ton corvette which sank near the tense maritime border with the Democratic People's Republic of Korea (DPRK) last month.

Workers using a giant offshore crane salvages portion of the sunken South Korean naval ship Cheonan off Baengnyeong Island, South Korea, Thursday, April 15, 2010. [Xinhua]

"There is a very high possibility that the sinking was caused by an external explosion rather than an internal explosion, but we will keep all the possibilities open for the final determination," said Yoon Duk-yong, co-head of the 38-member investigation team looking into the incident.

The warship broke into two parts after an unexplained blast on March 26 during a routine patrol off the western coast near the disputed maritime border with the DPRK, a scene of fatal naval skirmishes in the past.

Fifty-eight of the 104 sailors on board were rescued alive shortly after the sinking, So far, 38 bodies have been recovered, while eight sailors remain unaccounted for.

The investigation team conducted an initial inspection of the stern where most of the missing sailors were trapped inside the sunken ship after it was lifted out of the water on Thursday.

The country's defense minister Kim Tae-young, calling the incident "a serious national security issue," offered an apology to the public over perceived blunders in the military's responses in the wake of the incident.

He told parliament Wednesday that the military is considering both military and non-military means in response if initial allegations on the DPRK's possible involvement in the incident are confirmed to be true, but later withdrew his remark.