Divers must now rip through cabin walls of the submerged South Korea ferry to retrieve more victims as their grim work brought the official death toll to 146.

The victims were overwhelmingly pupils of a high school in Ansan, near Seoul. More than three-quarters of the 323 students are dead or missing, while nearly two-thirds of the other 153 people on board the Sewol when it sank a week ago survived.

Even with more than 150 people still missing, the funeral halls in Ansan are already full, Oh Sang-yoon of the government-wide emergency task force centre said. He said the centre "is taking measures to accommodate additional bodies by placing mortuary refrigerators at the funeral halls in Ansan" and directing mourning families to undertakers in nearby cities.

On Jindo island, where bodies recovered from the ferry are taken, descriptions of the dead are read over a loudspeaker. Relatives rush over to the main notice board and peer at details added by an official.

Some relatives cry out and run from the tent. Others stand red-eyed and shell-shocked.

The number of corpses recovered has risen sharply since the weekend, when divers battling strong currents and low visibility were finally able to enter the submerged vessel.

But task force spokesman Koh Myung-seok said the work was becoming more difficult and divers must now break through cabin walls to recover more bodies.

"The lounge is one big open space, so once in it we got our search done straight away. But in the case of the cabins, we will have to break down the walls in between because they are all compartments," Mr Koh said.

Twenty-two of the 29 members of the ferry's crew survived, and nine have been arrested or detained in connection with the investigation.

The captain, Lee Joon-seok, and two crew members were arrested on Saturday on suspicion of negligence and abandoning people in need. Four other crew members were detained on Monday and arrested yesterday. Another two crew members have been detained.

The four crew members arrested yesterdeay talked to reporters after a court hearing, their faces hidden with caps, hooded sweatshirts and masks.

One said they tried to correct the ferry's listing early on but "various devices, such as the balance weight, didn't work. So we reported the distress situation, according to the captain's judgment, and tried to launch the lifeboats, but the ferry was too tilted and we couldn't reach".

The captain has said he waited to issue an evacuation order because the current was strong, the water was cold and passengers could have drifted away before help arrived. But maritime experts said he could have ordered passengers to the deck - where they would have had a greater chance of survival - without telling them to abandon ship.

Bodies have mostly been found on the third and fourth floors of the ferry, where many passengers seemed to have gathered. Many students were housed in cabins on the fourth floor, near the stern of the ship.

The cause of the disaster is not yet known. Senior prosecutor Ahn Sang-don said investigators are considering factors including wind, ocean currents, freight, modifications made to the ship and the fact that it turned just before it began listing. He said authorities would stage a simulation and get experts' opinions.

The Ministry of Ocean and Fisheries had released incomplete data on the turn last week a central station did not receive all the signals the Sewol's on-board transponder had sent. It released more complete details yesterday with data received by another station, and those show that the ferry spent about three minutes making about a 180-degree turn shortly before it began to list.

It remains unclear why the ship turned around. The third mate, who was arrested on Saturday, was steering at the time of the accident, in a challenging area where she had not steered before, and the captain said he was not on the bridge at the time.

Shareholders of the Sewol's owner, Chonghaejin Marine, apologised in a statement saying they felt "infinite sadness and responsibility".

"We will humbly accept all responsibility for this accident and we will not hesitate to do anything to console the pain of victims and grieving families even a little bit," said the statement from Yu Dae-kyun, Yu Hyuk-gi and others who are de facto owners of Chonghaejin. The company's president apologised earlier.

In Ansan, a temporary memorial for the victims opened at Olympic Museum, near Danwon High School, which the pupils attended.

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