A third mate took the helm of the sunken South Korean passenger ferry at the last minutes before the ship sank into the waters off the country's southwestern coast, prosecutors said Friday.

"We have confirmed that the captain of the Sewol left the wheel to a third mate before the ship began sinking," chief investigator Park Jae-eok said at the West Regional Headquarters of the Korea Coast Guard in Mokpo, 410 kilometers south of Seoul.

The police and prosecutors have been questioning rescued captain and crew members to figure out why the 6,825-ton passenger ferry Sewol capsized and sank off Jindo Island, near the southwestern tip of the Korean Peninsula, at around Wednesday.

The 69-year-old captain came back to the steering room after the ship began tilting, prosecutors said.

The ferry's sinking was believed to have been caused by a sudden turn in direction.

The change in direction was believed to have moved some 180 cars and trucks and over 1,100 tons of shipping containers on the deck of the ship to one side, driving the ship to lean to the port side gradually.

The ship reportedly tilted first, rolled over on the port side and capsized before being totally submerged in the waters.