It said a 20 meter by 22 meter section of the ill-fated ship's structure is being cut open with the entire process to take four to five days to complete.

Search teams have almost completed checking the fourth floor of the ferry's rear section that can be reached. Since the ship was placed in dry dock earlier this month, workers have failed to find any remains, although they did retrieve mobile phones and belonging of people who perished when the 6,800-ton vessel capsized off the country's southwest coast and claimed 304 lives, most of them teenage students on a school trip to Jeju Island.

The hull has since been raised from the bottom of the sea and transported to Mokpo, a port located some 410 kilometers south of Seoul.

"There is still debate on the extent of removing parts of the hull to gain access and how best to conduct a search once search parties can enter the previously closed off part of the ferry," a sources said.

Besides gaining entry to the gallery, the latest work can allow search teams to go into cabin areas on the fourth floor where at least two people still missing had quarters. (Yonhap)