South Korean divers resumed searching Thursday for 290 people -- many of them teenagers -- missing nearly 24 hours after an ocean-going ferry capsized near an island off the South Korean coast.
Coast guard officials say six people were confirmed dead by early Thursday, and that 179 others had been rescued.
Authorities warn the death toll could spike sharply as rescuers probe the wreckage in waters 32 meters deep. Officials reported water temperature at just over 12 degrees Celsius -- a temperature cold enough to cause hypothermia in a matter of hours.
Dozens of helicopters and ships are involved in the search and rescue effort, and a U.S. naval amphibious assault ship remained on standby to provide support if requested.
The 6,825-ton ferry Sewol departed the port of Incheon, west of Seoul, Tuesday night for the island of Jeju, some 100 kilometers off the southwest coast. The vessel was also carrying about 150 cars and trucks.
Authorities have not established the cause of the sinking. But some survivors reported hearing a loud impact noise before the vessel rolled onto its side and began sinking.
Many of the passengers said they were initially told to stay in their seats and not try to escape.
Among the passengers were 325 students from a high school near Seoul, traveling to the popular resort island for a four-day field trip and sightseeing.
Heavy fog was reported in the area on Tuesday evening, but it is not known whether it contributed to the sinking.