A major search is continuing for 46 sailors missing after a South Korean naval ship sank near the disputed maritime border with North Korea.
South Korea says about 60 crew members have been rescued and it is hoped that some sailors could be alive in the hull of the upturned vessel.
A military spokesman said there was no indication so far that North Korea had been involved in the incident.
The boast sank off the west coast of the divided peninsula, in an area which has seen deadly exchanges of fire between the two countries' navies in the past.
The 1,200 tonne Cheonan was on a routine patrol near South Korea's Baeknyeong Island when it began sinking, the BBC reports.
Military officials told South Korea's Yonhap news agency that an explosion tore a hole in the rear hull, shutting off the engine and quickly taking the ship down.