South Korea's defence ministry said yesterday it was focusing its investigations on the intentions of the nine North Korean crew found dead in a midget submarine captured in its territorial waters earlier this week.
A spokesman also said Seoul had demanded that the North punish the personnel responsible for the intrusion and that a meeting of military officials be held at the earliest date.
The media had speculated that the dead men were returning from a trip to the South.
The Seoul Broadcasting System (SBS) television said sand was discovered on the crew's clothing. SBS quoted Mr Lee Kwang-su, sole North Korean survivor from a previous submarine incident, as saying it was unlikely the sand was from the north because North Korean submarine dockyards are relatively free of sand.
Adding to the speculation was the discovery of a soft drink bottle in the submarine which was a South Korean brand. North Korean agents have been known to carry South Korean-made products during espionage activities.
Earlier, the ministry said four of the nine dead men had gunshot wounds to their heads and the other five had multiple bullet wounds to their bodies.
"We found nine crew dead inside the submarine," said Maj Gen Chung Young-jin of Seoul's Joint Chiefs of Staff. "There were some signs of disagreement among themselves about the group suicide.
"It looks like the five were shot first in unaimed fire by the remaining four, who then killed themselves," Maj Gen Chung said.