JINDO, South Korea — Prosecutors detained four more crew members Monday from the South Korean ferry that sank last week, leaving more than 300 people dead or missing in one of the country’s worst peacetime disasters.

Three of the four ship’s mates who were on the ferry, the Sewol, when it tilted and capsized Wednesday were detained for possible criminal indictment, as was the ferry’s chief engineer. The engineer, who prosecutors identified only by his surname, Park, was one of the first members of the crew to leave the vessel as it was sinking, according to at least two crew members interviewed in recent days.

Prosecutors already arrested the Sewol’s captain, Lee Jun-seok, on Saturday, along with another ship’s mate and a helmsman.