SEOUL, April 18 -- South Korean coast guard and navy divers succeeded Friday in entering into the hull of a sunken ferry, two days after the ship carrying 475 people, mostly high school students, capsized off the country's southwestern coast.

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

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. local time 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.

The divers succeeded in entering the hull for the first time Friday morning. Survivors have not been found yet. Air started to be pumped into the hull to offer air to possible survivors.

Death toll kept rising, with 28 people confirmed dead and 268 others still missing. The number of the rescued remained unchanged at 179.

The passengers aboard the sunken 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 one 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.

The death toll could rise as hundreds of people were still missing two days after the 6,825-ton passenger ship "Sewol" capsized and sank off Jindo Island. Most of the missing were believed to be trapped inside the sunken vessel.

Two Chinese citizens were confirmed to have been aboard the sunken ferry, one male and the other female, on their way to Jeju Island for vacation.