Rescue workers retrieved 12 more bodies from a sunken ferry late Tuesday amid desperate search operations against rising tides and strong currents for the nearly 100 passengers still missing.

The bodies were recovered from the sunken ferry Sewol on Tuesday afternoon, raising the death toll to 205, according to the Coast Guard. Still, 97 passengers remain unaccounted for.

After recovering four bodies in overnight operations, Coast Guard, Navy and civilian divers have been struggling to search the inside the ill-fated ship that capsized on April 16 in waters off South Korea's southwestern island of Jindo.

Most of the victims found in the day were in the lobby of the fifth floor of the vessel, according to the state response team.

"Our job will focus on searching the right side of the fourth and fifth floor of the (five-story) boat ... as we've failed to gain access to the side because the ship sank with the right side on the bottom," its official said.

So far, rescue workers finished searching 38 out of 64 compartments where the missing passengers are believed to be trapped, he added.

Of 476 passengers aboard, mostly high school students on a field trip, 174 people, including the captain and most of the crew, were rescued shortly after the accident, but no one has been found alive since.

Search efforts, however, have been hampered by bad weather, strong underwater currents and high spring tides, which are known to have the widest tidal range.

Currents are stronger by about 40 percent during spring tides compared with a period of neap tides when the difference is the least.

The spring tides are expected to last until Friday, officials said.

A U.S. Navy recovery vessel, the USNS Safeguard, also arrived at the site of the shipwreck later in the day to help with recovery efforts. The ship had left from the southern port city of Busan on Monday.

To help make the search operations easier while minimizing expected injury or damage to those inside, the rescue team said it plans to employ fire-fighting equipment.

"We will use diverse fire-fighting gadgets to eliminate cargo inside the compartments that prevent us from entering the door," a team official said.

"We have not considered using explosives or wire cutters to break open doors, as they could hurt those inside," he added.

A diving bell, which is an airtight chamber used for transporting divers underwater, may also be put into operation later in the day.

President Park Geun-hye, meanwhile, visited the government's official mourning altar in Ansan, just south of Seoul, to pay her respects to the victims.

After laying a chrysanthemum and burning incense, she held a moment of silence after she observed rows of portraits mounted on the altar. In a brief meeting with the bereaved families, she faced their angry protests and tearful appeals over the government's poor management of the funeral process and the country's systematic irrationality, which led to the tragedy.

As of Tuesday, the altar displayed the photos of 162 victims, including 155 students and four teachers of Ansan's Danwon High School. Portraits have been added to the altar with each confirmed death.

Of all, 325 passengers were Danwon students on a field trip to the southern resort island of Jeju.

Thousands of thousands of people have visited mourning altars across the nation to pay tribute to the deceased.

Prime Minister Chung Hong-won, who has offered to step down over what many see as the government's poor handling of the disaster, was in Jindo where he was scheduled to meet with officials, including Oceans and Fisheries Minister Lee Ju-young, over the ongoing recovery efforts.

Park has said she will accept the resignation offer after the situation has been brought under control.

Investigators, meanwhile, looking into the cause of the deadly accident focused on studying material they seized from the situation rooms of the local Coast Guard and the regional fire department on Monday to determine whether they responded appropriately upon receiving the Sewol's distress call.

Investigators have also questioned officials from the ferry's operator and other related companies over possible irregularities and flaws in the vessel's modifications, cargo capacity and safety equipment.

Prosecutors have arrested the Sewol's 69-year-old captain, Lee Jun-seok, and about a dozen other crew members on suspicion of negligence of duty and abandoning passengers.

Crew members of the Sewol including captain Lee are suspected of making seven phone calls to the ferry operator before they escaped from the vessel, according to investigators.

Prosecutors and police said they are focusing on whether the ferry operator gave improper orders to the crew, including to abandon ship.

Meanwhile, the size of the crew was found to have been miscounted as four part-timers were not included.

Previously, investigators said that 29 crew members were on board, but four more part-timers were found to have been on the ferry. They had been classified as passengers, not crew members.

The probe also found that the crew had not received any training related to emergency escape such as the use of life jackets. As some crew members did not even know how to use a walkie-talkie, they were unable to tell the passengers to leave the ferry, according to the investigators.