Divers battled strong currents and murky waters Friday to finally enter a South Korean ferry two days after it sank, as investigators revealed the captain was not at the helm when the vessel capsized with hundreds on board.

South Korean prosecutors sought arrest warrants Friday for the captain and two crew members of the ferry, a coastguard official said.

The unfolding tragedy was compounded by the apparent suicide of a high school vice principal who had been rescued from the 6,825-ton Sewol that sank Wednesday with hundreds of his students trapped inside.

The confirmed death toll stood at 28, but the focus of concern remained on the 268 still unaccounted for. Of the 475 people on board when the Sewol capsized, only 179 were rescued and no new survivors have been found since Wednesday.

The Chinese Embassy on Friday confirmed a fourth Chinese citizen aboard the ship.

Earlier in the day, the embassy said that a Chinese schoolgirl, along with another two Chinese nationals, one male and the other female, was also on the ill-fated ship  and remained unaccounted for.

Exhausted dive teams, who waded through powerful currents, finally managed to access the interior.

After several attempts, two divers managed to pry open a door and enter the cargo section, a senior coastguard official said. Hours later another two-man team accessed one of the cabins, but found nothing.

Three giant, floating cranes reached the rescue site, but regional coastguard commander Kim Soo-hyun stressed they would not begin lifting the multi-deck ferry until they were sure there were no survivors inside. "I want to be clear: There won't be any salvage work done against the will of the families," Kim said.

AFP - Xinhua