Helicopters are seen above a South Korean passenger ship (C) that has been sinking, in the sea off Jindo April 16, 2014.[Photo/Agencies]

SEOUL/JINDO, South Korea  -- A passenger ship carrying more than 470 people, mostly high school students, sank off South Korea's southern coast on Wednesday, leaving at least two people dead, including one student, and more than 300 others missing.[Photos]

The government had earlier announced that 368 people were rescued, but officials later acknowledged there was an error in tallying up figures. More than 300 people still remain unaccounted for, they said.

Only about 180 have been rescued so far, more than five hours after the accident, officials said, amid growing fears that many of them could be trapped inside the sunken ship, though officials said some passengers could have been rescued by private fishing boats.

Cargo ship sinks off ROK, 9 die

Stranded cruise guests flown home

The 6,325-ton Sewol was carrying 477 people, including 325 students from a high school in Ansan, just south of Seoul, when it sent out a distress signal at 8:58 a.m. in waters 20 kilometers off the island of Byeongpoong, according to the Coast Guard.

The two dead were a 27-year-old female crew member and a high school student. The sailor was found dead in the ship while the student died after being rescued. Some 27 others were taken to hospitals with injuries, including broken bones and burns, officials said.

The accident prompted a massive rescue operation involving about 40 Coast Guard and military vessels and helicopters. Divers from the Navy's ship salvage unit (SSU) were also mobilized to search the sunken ship, officials said.

A US Navy amphibious assault ship equipped with two helicopters, which was on its routine patrol mission in the western sea, was moving to the scene to help with the rescue operation, US Forces Korea said.

Television footage showed the ship sinking on its side and rescue workers in orange uniforms trying to help passengers leave the vessel as helicopters were flying overhead. Rescued passengers were wrapped in beige blankets one by one after arriving at a nearby port.

The ill-fated ship completely capsized and sank in two hours.

The cause of the accident was not known, though survivors said they heard a banging noise before the ship suddenly started sinking. Speculation has arisen that the ship might have hit an underwater rock or collided with another vessel.

"There was a bang and then the ship suddenly tilted over," said a survivor identified by his surname Yoo, 57. "Downstairs were restaurants, shops and entertainment rooms, and those who were there are feared to have failed to escape."

The government said the priority is rescue operations.

"We will try to determine the cause of the accident after rescue operations are over," said Second Vice Home Affairs Minister Lee Gyeong-og said during a press briefing in Seoul.

Lee said the government will mobilize all available resources to search for the missing.

The ferry set off from the western port of Incheon on Tuesday evening later than scheduled due to dense fog, and was to arrive at the southern resort island of Jeju later on Wednesday. The students were on their way to Jeju for a four-day school trip.

The ship, which plies between Incheon and Jeju twice a week, was built in 1994, is 146 meter long and 22 meter wide, and has the maximum capacity of carrying 921 people, 180 vehicles and 152 shipping containers at the same time.

South Korean President Park Geun-hye ordered maximum efforts to rescue all of the passengers, stressing that all available Navy, Coast Guard and other vessels nearby should be mobilized to makes sure that not a single life is lost, presidential spokesman Min Kyung-wook said.

In a phone call to Coast Guard chief Kim Suk-kyoon, Park also ordered the mobilization of Coast Guard commandos to search every corner of the vessel to ensure that no one is left behind, the spokesman said.

There were no Chinese passengers on board the vessel, according to the Chinese Embassy in South Korea.

Cargo ship sinks off ROK, 9 die