By Jung Sung-ki

A multinational team of investigators failed to find traces of explopsives on the propeller of a torpedo collected from the site of the sinking of the Cheonan ship in March, according to a head of the team.

This, critics say, leaves lingering questions about the exact cause of the incident that killed 46 sailors.

The Joint Civil-Military Investigation Group (JIG), released its final report of the Cheonan investigation both in Korean and English Monday, following its interim report announced May 20. The group included experts from the United States, the United Kingdom, Australia, Sweden and Canada.

The 300-page final report contains records of the incident, the raising of the wreckage, the collecting of evidence and simulations.

“The ROK Navy ship Cheonan was sunk by a North Korean torpedo attack while conducting a normal mission in the vicinity of Baengnyeong Island at 09:22 p.m. on March 26, 2010,” the English-version of the report says in its conclusion.

“The analysis on the cause of the sinking initially left open every possibility and explored the possibilities of a non-explosion, internal explosion or external explosion for causing the sinking,” it says. “However, a detailed investigation following the salvage of the ship eliminated the possibilities of a non-explosion and internal explosion, leading the JIG to assess that an external explosion, and more specifically an underwater explosion, was the most likely cause behind the sinking.”

It says the possibility of a moored mine was not excluded.

“The Cheonan was split and sunk due to a shockwave and bubble effect generated by the underwater explosion of a torpedo. The detonation location was three meters to port from the center of the gas turbine room and at a depth of 6-9 meters,” it says.

The weapons system used in the attack was a CHT-02D torpedo with approximately 250 kilograms of explosives manufactured and used by North Korea, according to the report.

Maj. Gen. Yoon Jong-sung, head of the Ministry of National Defense’s Criminal Investigation Command, said the JIG had found a total of 36 traces of explosives consisting of RDX, HMX and TNT on the wreckage of the Cheonan.

But there were no such traces on the pieces of a torpedo found at the site of the incident, Yoon admitted. The JIG has called the torpedo parts one of the “decisive” pieces of evidence that prove North Korea’s involvement in the naval disaster.

Critics have cast doubts about the authenticity of the evidence presented by the investigators.

For example, the investigation team argued the “No. 1” inscribed in Korean on the propulsion section of the raised torpedo as conclusive evidence, but critics raised questions about how the lettering remained intact despite the heat of the explosion.