Meanwhile, the coast guard said it was investigating whether the ferry's captain was one of the first ones off the sinking ship.
The first instructions from the captain were for the passengers to put on life jackets and stay put, and it was not until about 30 minutes later that he ordered an evacuation, Oh Yong-seok, a 58-year-old crew member, told The Associated Press.
Several survivors also told the AP that they never heard any evacuation order.
The loss of that precious time may have deprived many passengers of the opportunity to escape as the Sewol sank Wednesday, not far from the southern city of Mokpo.
Twenty people, including a female crew member, at least five students and two teachers, were confirmed dead by coast guard officials Thursday night.
But the toll was expected to jump amid fears that more than 280 missing passengers, many high school students, were dead. Coast guard officials put the number of survivors today at 179.