South Korean coast guard and navy divers will seek to enter into the hull of the sunken South Korean passenger ferry for three hours late Friday after failing to make their way into passenger cabins earlier.

A total of 21 divers will try to pry their way into passenger compartments on the third floor of the five-story ship from 7 p.m. to 10 p.m., local broadcaster YTN reported, citing the South Korean Coast Guard.

Two divers opened the door of freight compartments on the second floor at 3:26 p.m. for the first time, two days after the ferry carrying 475 people, mostly high school students, capsized off the country's southwestern coast.

The divers, however, have withdrawn from the hull as the entrance into cabins was jammed with too many goods.

The second floor is comprised of freight compartments and there is a dining room on the first floor. The third and fourth floors are composed of passenger cabins where possible survivors were believed to be trapped.

About 87 passengers stayed at the cabins on the third floor, with 353 people put up on the fourth floor and seven on the fifth floor.

Search and rescue operations into the hull were made possible as the work of pumping air into the ship ended earlier.

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.

Rescue conditions were expected to worsen from Saturday afternoon as strong winds were forecast to blow. The wind speed will rise to 8-12 m/sec Saturday afternoon from 6-9 m/sec in the morning at the site of the accident.

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

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

Among the rescued, 75 were students from the Danwon High School in Ansan, a Seoul suburb. Eleven students have been confirmed dead, with 239 others still missing.

Three large salvage ships arrived at the scene Friday morning to pull the ship out of the waters, and another one got 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 airplanes and 173 rescue ships were deployed for search and rescue operations.

The death toll could surge as hundreds of people were still missing two days after the 6,825-ton passenger ship Sewol capsized and sank off Jindo Island near the southwestern tip of South Korea. 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.