Early reports indicate that a navigation error is the likely cause in a South Korea ferry's sinking. The tragedy has left four dead and 292 persons unaccounted for.
Officials stated that 164 people were rescued from the ferry, and survivors reported hearing and feeling an impact large enough to stop the boat.
"We heard a big thumping sound and the boat stopped," a survivor told South Korea news channel YTN. "The boat is tilting and we have to hold on to something to stay seated."
The ferry may have hit rocks, reef, or other objects in the water that damaged its hull. Objects in the water would have been harder to see because of the murky conditions.
"There is so much mud in the sea water and the visibility is very low," Vice Minister of Security and Public Administration Lee Gyeong-og told BBC.
One passenger told YTN that the ferry was "tilting and shaking" as it began to capsize and take on water.
Passengers on the lower decks would have had limited time to flee as the rushing water blocked escape routes.
One survivor, Kim Seung Mok, stated that he tried to help as many other passengers as he could.
"I stayed till the last to rescue people at the hall," he told YTN. "But the water was coming in so fast [that] some didn't make it out."
Over 300 passengers were students at Seoul's Ansan Danwon High School. 15 teachers from the school were also on-board.
Officials are focusing on the rescue mission at this time, as opposed to exploring what caused the ferry to sink.