South Korean investigators have said they believe an external explosion was the most likely cause of last month's sinking of a naval ship close to the disputed border with North Korea.

The sinking of the 1,200 ton patrol vessel Cheonan on March 26 left 46 sailors missing and feared drowned.
Another 58 crew members were rescued.
""There is a high possibility of an external explosion rather than an internal explosion,"" Yoon Duk-yong, the chief investigator, said in Seoul on Friday.
His comments came a day after salvage workers raised the stern of the sunken ship from the sea bed, retrieving 38 bodies.
The remaining two-thirds of the ship, which was torn in two by the explosion, is expected to be raised next week.
The news is likely to fuel speculation of North Korean involvement in the sinking, possibly from a torpedo or mine, although South Korean officials have cautioned against jumping to conclusions.