JINDO, South Korea, April 21 -- Death toll rose to 64 Monday morning in the South Korean ferry sinking accident as divers kept entering inside the hull of the submerged vessel while ships were scouring the waters.

So far, 64 people have been confirmed dead with 238 others still missing. The number of the rescued remained unchanged at 174.

The pan-government response center will hold a regular press briefing at 10 a.m. local time to explain overnight rescue operations.

Unmanned submersibles called remotely-operated vehicle were sent to enter the hull on the bow side and search possible survivors.

Jigging fishing boats, which catch squids, worked at the scene overnight to offer lightening for nighttime search and rescue operations.

Divers extended guideline ropes on the stern side to strengthen rescue operations there. Five ropes were installed Sunday near the submerged vessel to guide divers against rapid currents to the underwater gate of the ferry. The ropes enabled divers to enter the hull at a faster pace than before.

Divers entered inside the hull along their respective guideline ropes simultaneously, resulting in random discovery and retrieval of bodies trapped inside the ship.

Rescue operations are expected to pick up speed Monday given favorable weather conditions at the scene. Waves are forecast to be 0.5-1 meter high, with the wind to blow at a speed of 6-9 m/s. Water temperature in the area is at around 12 degrees Celsius.