South Korea's defense minister says a torpedo was the likely cause of an explosion that sank a warship near the tense border with North Korea last month.

Defense Minister Kim Tae-young told reporters Sunday that he believes a bubble jet effect caused by a heavy torpedo is the most likely cause of the disaster.

A bubble jet is a powerful shock wave and high-pressure gas bubble resulting from an explosive device detonating beneath a vessel.

Kim was also quoted by the French news agency as saying "various other possibilities are also under review."

Investigators say there is evidence that the 1,200-ton Cheonan patrol ship exploded because of a strong impact from the outside. Seoul has refrained from blaming Pyongyang for the incident until its experts carry out a thorough investigation. Pyongyang has denied any involvement.

South Korea raised the front section of the warship with a large crane Saturday.

A body was found inside the recovered section, bringing the official death toll to 40. Six sailors remain missing and are believed dead. The coast guard rescued 58 crew members from waters near the blast site.

There were 104 sailors on board the ship when it exploded and sank March 26 during a regular patrol in the waters near the disputed border with North Korea.

North Korea Saturday warned the United States and South Korea that it will employ "all means, including the nuclear deterrent" if they intrude into its territory. The state-run Korean Central News Agency quotes army chief Ri Yong-Ho as saying North Korea's armed forces are "fully ready to frustrate any provocation of the aggressors at a single blow."

U.S. Secretary of State Hillary Clinton Friday urged Pyongyang not to "engage in provocative actions," and said she hopes there is no "miscalculation" or action that could lead to conflict.

Voice of America