The captain and some crew members of the sunken South Korean ferry committed “unforgivable, murderous acts”, President Park Geun-hye said yesterday.
The disaster left more than 300 people dead or missing.
The captain initially told passengers to stay in their rooms and waited more than half an hour to issue an evacuation order as the Sewol sank.
But the ship had tilted so much by that time that many of the estimated 240 people missing are believed to be trapped inside.
Ms Park said the captain and crew “told the passengers to stay put but they themselves became the first to escape, after deserting the passengers”.
She said that “legally and ethically, this is an unimaginable act.
Earlier, four more crew members were detained on allegations of failing to protect passengers.
Prosecutor Ahn Sang-don said two first mates, one second mate and a chief engineer had been accused of abandoning the ship. The ferry’s captain, Lee Joon-seok, 68, and two other crew members have been formally arrested on suspicion of negligence and abandoning people in need.
A total of 64 bodies have now been recovered from the vessel.
A radio transcript revealed the ferry was crippled by confusion and indecision well after it began listing.
The ship sank with 476 people on board, many of them students from one high school.
The cause of the disaster is not yet known, but prosecutors have said the ship made a sharp turn before it began to list.
More than 170 people survived the sinking of the Sewol, which had been on its way from the South Korean port city of Incheon to the southern island of Jeju.