Lee Joon-seok, the captain of South Korean ferry Sewol that capsized and sank earlier this week has been arrested, Yonhap news agency reports.
Captain Lee Joon-seok faced charges including negligence of duty and violation of maritime law.
Yonhap said a local court had issued arrest warrants for him and two other crew members on these charges.
Efforts to find the 268 people still missing have been hampered by low visibility and strong currents.
Twenty-eight people are now known to have died in the disaster, with 179 rescued.
The ferry Sewol was sailing from Incheon, in the north-west, to the southern resort island of Jeju. It capsized and sank within two hours.
Lee Joon-seok, who had already been questioned by police, was shown on television on Thursday, his face partially obscured, apologizing to the victims and their relatives.
“I am really sorry and deeply ashamed. I don’t know what to say,” he said.
It has emerged that a junior officer – and not the captain – was at the helm of the ferry when it capsized.
Investigations are focusing on the sharp turn the vessel took before it started listing and whether an evacuation order could have saved lives.
Some experts believe such a tight turn could have dislodged heavy cargo and destabilized the vessel, while others suggest it could have been caused by a collision with a rock.
Survivors have accused the crew of instructing them to remain where they were rather than evacuate the ship.
Messages and phone calls from those inside painted a picture of people trapped in crowded corridors, unable to escape the sharply-listing ferry.
Earlier on Friday, coastguard officials said that two divers had managed to enter the cargo bay of the vessel, but could not identify or rescue anyone because of items obstructing their way.
Some 350 of those on board were students from Danwon High School in Ansan, a suburb of Seoul, who were on a school outing when the ferry sank.
The vice principal of Danwon High School, who was rescued from the ferry, was found dead on nearby Jindo island on Friday.
Kang Min-Kyu, 52, had been missing since Thursday and was discovered hanging from a tree near the gym on Jindo island – where many of the relatives of missing passengers have been staying.
Amid a major search and rescue operation, officials say air has been pumped into the ship to help any people trapped inside and to help refloat the vessel. But officials say it is unlikely anyone has survived.
Three salvage cranes have reached the site and they may be used to raise the ship or move it to another area with weaker currents.
Challenging conditions have hampered the search for a third consecutive day.
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