Rescue boats and helicopters scrambled Wednesday to find almost 300 passengers, including scores of high school students, missing after a ferry sank off the southwest coast of South Korea.
Of the 459 people on board, 164 have been rescued, the security ministry said.
Many jumped from the listing ship to the freezing waters of the Yellow Sea.
The bodies of at least four people - a female and three males– were confirmed dead. About 292 remain unaccounted for, the ministry said.
The rescue operation was still underway Wednesday evening, hours after the ferry first sent out a distress signal.
Authorities could not immediately say what caused the ship to sink. The weather at the time of the incident was clear.