South Korean Ferry Captain Lee Joon Seok Investigated
A vessel involved in salvage operations passes near the upturned South Korean ferry "Sewol" in the sea off JindoReuters

Prosecutors have requested an arrest warrant for the captain of the South Korean ferry which capsized, leaving 25 dead and hundreds missing.

The request comes as investigators found that Captain Lee Joon-Seok was not at the helm of the ship when it capsized.

"He may have been off the bridge... and the person at the helm at the time was the third officer. The captain was not in command when the accident took place," an investigator told a news conference.

Prosecutor Park Jae-Eok has said the enquiry is exploring the possibility that the third officer ordered the vessel to make an abrupt turn, causing it to tilt and take on water.

It has also been revealed that the 68-year-old captain delayed evacuation of the ferry for half an hour after the distress signal was sent.

Helmsman Oh Yong-Seok said the ship was already listing more than five degrees - the critical angle at which a vessel can be brought back to even keel -when the crew gathered on the bridge and sent a distress call.

Relatives check the survivor lists at Jindo portGetty

According to Yong-Seok, passengers were instructed to stay where they were. He revealed it was a further half hour before Captain Joon-Seok finally gave the order to abandon ship, however it is not known whether the order was relayed to the passengers.

Several survivors have said they did not hear any evacuation orders from the Captain or the crew.

By the time the order was given, the ship had tilted to such an acute angle it was impossible for crew members to move to passengers' rooms to help them.

The evacuation delay also prevented lifeboats from being deployed in time. It is believed that had the Captain issued the order sooner, more lives could have been saved.

Captain Joon-Seok, who was among the 29 crew members and 20 passengers who survived the incident, appeared before assembled media and made a brief, videotaped message expressing his regret at the tragedy.

"I am really sorry and deeply ashamed. I don't know what to say," he said.

Two other crew members are also being sought after the court appeal on Friday. No charges have been specified.

A total of 475 people, including 325 students, were aboard the Sewol as it sank near the southern city of Mokpo.

The ferry was on a 14-hour journey from Incheon, in the northwest of the country, to the tourist island of Jeju.

The South Korean coast guard said 179 people have been rescued alive so far.

The current confirmed death toll is 25, but that figure is expected to rise sharply with 270 people still missing.

325 of the passengers were students from Danwon High School near Seoul who were on a field trip.