Prosecutors and police also said Friday they have asked a court to issue arrest warrants for the captain and two other crewmembers.
Besides the teacher, at least 28 people are now confirmed dead from the ferry, the Sewol, which sank Wednesday. Officials said there were 174 survivors and about 270 people remain missing, many of them high school students. With the chances of survival becoming slimmer by the hour, it was shaping up to be one of South Korea's worst disasters, made all the more heartbreaking by the likely loss of so many young people, aged 16 or 17.
The ship had left the northwestern port of Incheon on Tuesday on an overnight journey to the holiday island of Jeju in the south with 476 people aboard. It capsized within hours of the crew making a distress call to the shore at 9 a.m. Soon, only its dark blue keel jutted out over the surface. By late Friday, even that had disappeared, and rescuers floated two giant beige buoys to mark the area. Navy divers attached underwater air bags to the 6,852-ton ferry to prevent it from sinking further, the Defense Ministry said.
Coast guard officials said divers began pumping air into the ship in an attempt to sustain any survivors.
On Jindo's shore, angry and bewildered relatives watched the rescue attempts. Some held a Buddhist prayer ritual, crying and praying for their relatives' safe return.
"I want to jump into the water with them," said Park Geum-san, 59, the great-aunt of a missing student, Park Ye-ji. "My loved one is under the water and it's raining. Anger is not enough."
The school vice principal found hanging was identified as Kang Min-kyu. In his suicide note, Kang said he wanted to take responsibility for what happened because he had led the trip, according to police. He asked that his body be cremated and the ashes scattered at the accident site.
South Korean officials offered some information about what may have led to the sinking. They said the accident happened at a point where the ferry had to make a turn. Prosecutor Park Jae-eok said investigators were looking at whether the third mate ordered a turn that was so sharp that it caused the ship to list.
The ship made the sharp turn between 8:48 a.m. and 8:49 a.m., but it's not known whether that was done voluntarily or because of some external factor, said Nam Jae-heon, a spokesman for the Maritime Ministry.
Another angle being probed is the role of the captain, 68-year-old Lee Joon-seok.
Yang Jung-jin, a senior prosecutor, said the captain was not present on the bridge when the ship was passing through an area with many islands clustered closely together, something he said is required by law so the captain can help a mate make a turn. The captain also abandoned people in need of help and rescue, he said.
"The captain escaped before the passengers," Yang said.
Two crewmembers on the bridge of the ferry — a 25-year-old female mate and a 55-year-old helmsman — also failed to reduce speed in the waters near the islands and conducted a sharp turn, Yang said. They also did not carry out necessary measures to save lives, he said.
A transcript of a ship-to-shore radio exchange and interviews by The Associated Press showed the captain delayed the evacuation for half an hour after a South Korean transportation official told the ship it might have to evacuate.
The recommendation by the unidentified official at the Jeju Vessel Traffic Services Center came at 9 a.m., just five minutes after a distress call by the Sewol. In the exchange, the Sewol crewmember says: "Currently the body of the ship has listed to the left. The containers have listed as well."
The Jeju VTS officer responds: "OK. Any loss of human life or injuries?" The ship's answer is: "It's impossible to check right now. The body of the ship has tilted, and it's impossible to move."