Rescue workers race to save passengers from the South Korean ferry Sewol on April 16. Captain Lee Jun-seok is under investigation for disguising himself as a passenger to abandon the ship as it sank. Photo: CFP

The confirmed death toll from South Korea's ferry disaster passed 100 on Tuesday as divers sped up the grim task of recovering scores more bodies from the submerged ship in relatively improved weather and calm seas.

The official death toll rose to 121 while 181 others were still missing after divers recovered nine bodies from the wreckage. The number rescued remained at 174. Seven days into the search after the ferry went down on Wednesday, no survivors or survival signals have been reported.

When referring to three foreign bodies, which were retrieved on Monday night, the spokesman said the authorities informed the Chinese embassy of the two bodies being Chinese men, but he said that the third body, which was earlier said to be a Russian, had yet to be confirmed.

A South Korean court official said Tuesday that warrants to formally arrest four crew members of the ferry had been issued, as prosecutors and police continued their investigation into the disaster, the South Korean Yonhap News Agency reported.

A judge from the court revealed that two first mates, a second mate and a chief engineer of the ferry should be held in custody, according to Yonhap. Seven crew members including the captain have been arrested.

The tax authorities launched a special inspection into the family of the ferry's owner on Tuesday, raiding offices of the operator and its affiliates. The tax agency reportedly planned to investigate documents and computers seized for possible tax evasion and slush funds.

An official at the Financial Supervisory Service told Reuters it was investigating whether the owner's company or family engaged in any illegal foreign transactions.