(CBS News) SEOUL, South Korea -- All 15 people involved in navigating the South Korean ferry that sank and left more than 300 people dead or missing are now in custody after authorities on Saturday detained four more crew members, a prosecutor said.
Yang Jung-jin of the joint investigation team said two helmsmen and two members of the steering crew were taken in on preliminary arrest warrants issued late Friday. Eleven other crew members, including the captain, had been formally arrested earlier.
All are accused of negligence and of failing to help passengers in need as the ferry Sewol sank April 16. The captain initially told passengers to stay in their rooms and took half an hour to issue an evacuation order, by which time the ship was tilting too severely for many people to get out.
Ten days after the sinking, 187 bodies have been recovered and 115 people are believed to be missing, though the government-wide emergency task force has said the ship's passengers list could be inaccurate. Only 174 people survived, including 22 of the 29 crew members.
The seven surviving crew members who have not been arrested or detained held non-marine jobs such as chef or steward, Yang said in a telephone interview from Mokpo, the southern city near the wreck site where prosecutors are based. A court hearing was held Saturday to determine whether formal arrest warrants will be issued against the four newly detained crew members.
South Korean television aired video of the police escorting the four men to court. All four wore baseball caps that hid their faces, and at least one was limping.
Capt. Lee Joon-seok told reporters after his arrest that he withheld the evacuation order because rescuers had yet to arrive and he feared for passengers' safety in the cold water. Crew members have also defended their actions.
Helmsman Oh Yong-seok, one of those arrested Saturday, has said he and several crew members did their best to save people. He said that he and four crew members worked from nearby boats to smash windows on the sinking ferry, dragging six passengers stuck in cabins to safety.
Officials in charge of the search effort said Saturday that divers have reached two large rooms where many of the lost may lie dead, but the search had to be suspended because of bad weather. Currents were already strong Saturday morning, as they were in the first several days of the search, when divers struggled in vain even to get inside the submerged vessel.
"This morning (the divers) did a primary dive, but because of the strong current they were losing their masks, so we have stopped the dive for now," Kim Jin-hwang, a South Korean navy official in charge of commanding the dive search, said in a briefing at Jindo. He said the search would resume once conditions improve.
CBS Radio News' Don Kirk reports from Seoul that weather conditions are not likely to improve until early next week, raising fears that some bodies may drift away and never be recovered.
The two rooms where searchers hope to find more of the missing soon are sleeping units designed for many people - one in the stern and one in the bow. Fifty students from Danwon High School in Ansan were booked into one of them. Students from the city near Seoul make up more than 80 percent of the dead and missing; they had been on their way to the southern tourist island of Jeju.
Large objects that toppled when the ferry tipped over and sank are believed to be keeping divers from reaching bodies in at least one of the rooms.
"Many structures ... all fell down as the ship listed, and now are all buried on the left side. Because of the weighty objects it was impossible to entirely search the room," Kim said.
Also Saturday, the Ministry of Oceans and Fisheries said it would soon change ferry systems so that passenger, vehicle and cargo information is processed electronically. There is not only uncertainty about how many people were on the Sewol, but a huge discrepancy regarding the amount of cargo it was carrying when it sank.
The ministry said in an email that starting June 1, passengers' names, genders, birthdates and contact information will be electronically entered when they get their boarding passes. Vehicles and cargo will be electronically processed beginning July 1, the ministry said.
The Sewol was carrying an estimated 3,608 tons of cargo, according to an executive of the company that loaded it. That far exceeds what the captain claimed in paperwork - 150 cars and 657 tons of other cargo, according to the coast guard - and is more than three times what an inspector who examined the vessel during a redesign last year said it could safely carry.
Lee Kyu Yeul, professor emeritus in ship and offshore plant design at Seoul National University's Department of Naval Architecture and Ocean Engineering, said the reported load could have set the ship tipping over with a significant turn. Tracking data show the ship turned 45 degrees before sinking, and crew members have reportedly said that they had tried to make a much less severe turn.
Yang, the prosecutor, said that the cause of the sinking could be due to excessive veering, improper stowage of cargo, modifications made to the ship and tidal influence. He said investigators would determine the cause by consulting with experts and using simulations.
Prosecutors have conducted several raids to seize documents and have ordered a few dozen people not to leave the country.
The Korean Register of Shipping and the Korea Shipping Association, which regulates and oversees departures and arrivals of domestic passenger ships, both were raided, according to officials at both organizations who spoke on condition of anonymity because they were not authorized to speak about matters under investigation.
The shipping association issued a statement Friday saying that its chief director, Joo Sung-ho, intends to resign. Joo expressed his regrets over the accident and hoped that with lessons learned from the sinking, "our country will become a safe place without accidents," the statement said.
President Obama arrived Friday at the Blue House, South Korea's presidential residence, and presented President Park Geun-hye with an American flag that flew over the White House the day the ship sank. Mr. Obama's first South Korean visit since Park took office last year was aimed at issues including North Korea, but he noted that his trip comes at a time of "great sorrow."
"So many were young students with their entire lives ahead of them," Mr. Obama said, invoking his two daughters, both close in age to many of the ferry victims. "I can only imagine what the parents are going through at this point, the incredible heartache."
Mr. Obama also said he was donating a magnolia tree from the White House lawn to Danwon High School in honor of the lives lost, and as a symbol of friendship between the U.S. and South Korea.