The toll in the sinking of a ferry, carrying 475 people, mostly high school students, in sea waters off South Korea's southwest coast, rose to 28 Friday, officials said.

South Korean Coast Guard and Navy divers succeeded Friday in entering into the hull of the sunken ferry, two days after the ship capsized, Xinhua reported.

The divers secured a path to the dining room of the submerged vessel, and found various passages to pry their way into the hull.

Kim Seok-kyun, head of the South Korean Coast Guard, told reporters that divers will go into the restaurant and compartments from 3 p.m. to search for possible survivors.

Maritime police and military divers tried 20 times overnight to make their way into the submerged hull, but they failed due to rapid currents, low underwater visibility and high waves.

Survivors have not been found yet. Air started to be pumped into the hull to offer air to possible survivors.

The toll has kept rising, with 28 people confirmed dead and 268  still missing. A total of 179 were rescued.

The passengers aboard the vessel included 325 high school students and 15 teachers on a four-day field trip. The ship departed South Korea's western port city of Incheon Tuesday night for the southern resort island of Jeju.

Among the rescued, 75 are students from the Danwon High School in Ansan, a Seoul suburb.

Three large salvage ships arrived at the scene Friday morning to pull the ship out of the water, with another set to get there in the evening. It was expected to take over a month to salvage the submerged vessel.

A total of 535 coast guard and navy divers were working at the scene, and 31 aircraft and 173 ships were deployed for search and rescue operations.