South Korean Prime Minsiter Chung Hong-won has urged rescue crews to put all of their energy into saving as many lives as they could, as the search for the missing continues.

(Act 1 Chung, male, Korean)

"As of now, we don't have any minute or second to waste. We have to use all our energy to rescue more lives. Therefore I ask every leader of each department to stay on the scene and conduct their team, and do their best to fulfil their responsibility."

Meanwhile, the ship's operator, Chonghaejin Marine, has apologized for the accident and vowed to focus on rescue efforts.

About 180 divers were sent to the scene during the night, as most of those missing are believed to be trapped inside the sunken vessel.

72 rescue ships and 14 helicopters are also searching the surrounding waters.

A U.S. navy ship with helicopters on board is on its way to the scene to join the search operation.

325 people on board the passenger ship were high school students, who were on a school excursion.

(Act 2 Student, male, Korean)

"There was an announcement telling us to sit still, but the ferry was already sinking. Some of the students were not able to escape. The ferry started to list, so we asked if we should escape now, but the announcement kept telling us to stay still. I'm so worried about the students in rooms."

The ferry, which sailed from the western port city of Incheon for the resort island of Jeju, sent a distress call on Wednesday morning after it began listing to one side.

The cause of the sinking is still under investigation.

But the vessel is believed to have run aground, as some passengers said the ship began leaning after a thumping sound on the bow.

The high number of people unaccounted for, likely trapped in the ship or floating in the ocean, has raised fears that the death toll could rise drastically.

Local official says the water temperature in the area is about 12 degree Celsius, cold enough to cause signs of hypothermia after more than one hour of exposure.

For CRI, I am Yu Yang.