Probe Shows How S. Korean Warship Blew Up

Investigators have concluded that a North Korean torpedo with a 500-pound-warhead hit and destroyed the South Korean Navy vessel, Cheonan.

In a show of force, the aircraft carrier USS George Washington arrived in South Korea Wednesday. It is expected to take part in military exercises next week.

Secretary of State Hillary Clinton traveled to the demilitarized zone Wednesday between North Korea and South Korea with Defense Secretary Robert Gates to announce plans to impose new sanctions against the north.

When investigators raised the severed hull and brought it back to port, readings from seismic stations, testimony of surviving sailors and analysis of the bent and twisted metal all led to the conclusion the Cheonan had been sunk by a torpedo with a 500-pound warhead.

Remnants of a torpedo from the ocean bottom showed corrosion on the metal parts indicating it had been underwater from about the same time the Cheonan was sunk, and its design exactly matched that of a North Korean torpedo.

It was an act of war although the North Koreans deny they did it. North Korea asked the UN for a new investigation into the sinking using their own team. South Korea on Thursday rejected the North's proposal for direct military talks, saying the issue should be handled under the armistice which ended their 1950-53 war.

Investigators from the U.S. and South Korea used an out-of-service Australian warship for target practice with a heavy weight torpedo to determine what happened to the Cheonan, which was ripped in two last March off the west coast of the Korean peninsula