SEOUL, April 30 (Xinhua) -- The first round of search and rescue operations for the South Korean ferry, Sewol, which capsized and sank off the country's southwestern coast on April 16, are expected to be concluded by May 15, South Korea's government- wide disaster response headquarters said on Wednesday.
The headquarters said the joint search and rescue team focused search operations on the front and central parts of the fourth floor and the lobby on the fifth floor on Wednesday, where most of the missing passengers are believed to be in.
The search operation will then be expanded to those cabins whose entrances have not been opened by May 6. The search and rescue team will wrap up the first round of operation by the middle of May after searching other areas where missing passengers may gather.
On the 15th day of search, floating objects and poor visibility, along with fast currents and high tides, are still hampering the search for bodies trapped inside the hull.
A diving bell, the device that can create an air-filled space for divers to rest and resupply for helping them dive deeper and stay longer in the sea was ready to be deployed for underwater search operation, authorities said.
The 33-hundred-ton U.S. Navy recovery vessel, USNS Safeguard, which is used for rescue and salvage, has also been operating at incident area.
At least 212 people have been confirmed dead and 90 others remain missing. No one has been rescued since 174 people were saved on April 16.
The Sewol ferry had 476 passengers aboard on its final voyage, most of them students and teachers.
A total of 70 high school students that survived the ferry accidents were discharged from the Korea University Ansan Hospital on Wednesday as their condition had notably improved, hospital officials said. But they will continue to receive psychological treatment.
South Korean President Park Geun-hye made an official apology during a cabinet meeting on Tuesday for the ferry sinking disaster, saying she was "sorry to the people and heavy hearted that many precious lives were lost."
She also apologized for the government's failure to prevent the accident in advance and for its insufficient initial response to the accident.
But many families of the victims rejected the apology, saying an apology made before several cabinet members behind closed doors can not be considered an apology and demanding Park make a public apology.
Meanwhile, investigators combined with prosecutors and police in the port city of Mokpo on Wednesday said overloaded cargo and illegal changes in the structure of the ferry may be responsible for the disaster.
Investigators said they have secured testimonies through questioning the crew members of the ship's operator Chonghaejin Marine Co., finding out that Sewol carried 3,606 tons of freight and cars, more than three times its recommended maximum cargo.
The 476 passengers aboard the ship were nearly half the maximum capacity. Chonghaejin Marine was responsible for adding overload cargo to compensate for its decreasing passenger revenue.
The 6,825-ton Sewol departed around two and a half hours later than scheduled from the western port city of Incheon, where other ships delayed their departure due to a heavy fog.
The ship, which was built in Japan in 1994 and had encountered no accidents for 18 years, was modified by the operator to expand passenger cabins and raise the total capacity including crew by 116 people to 956.
The investigation team is also looking into whether the ferry was safe for operation after a redesign early last year and whether the ferry carried enough ballast water to balance the overloaded ship.
In addition, investigator suspected that the ship owner has made some additional changes to the ship's structure besides its early redesign that has been approved.
As part of the enlarging investigation into corruption allegations related to the owner's family, prosecutors on Wednesday summoned Song Kook-bin, a chief of local door-to-door sales company Dapanda Co., who was one of the seven close aides to Yoo Byung-eun, head of Chonghaejin Marine Co.
South Korea's Board of Audit and Inspection (BAI) on Wednesday said it has launched a preliminary investigation into government agencies related to the accident - the ministries of maritime affairs, public safety, the Coast Guard and South Korea Maritime and Port Administration - on how they have been managing the operation of ships, their disaster management system and the way they have dealt with the Sewol accident.
BAI Officials said they have sent staff to those agencies to collect information. Documents received from these agencies will be reviewed in the following days. Whether to launch an official inspection into the agencies is based on the results of the preliminary probe.