The investigation into Yoo Byung-eon is making rapid progress, with prosecutors grilling key associates of the de facto owner of the operator of the sunken ferry Sewol.
On Wednesday, the prosecutors investigating alleged criminal activities of Yoo and members of his family questioned Song Kook-bin, chief of door-to-door sales company Dapanda Co., as a suspect in the expanding case.
Song is one of Yoo's seven closest associates. The seven, of whom three have now been questioned, hold various high-level positions in companies effectively owned by the Yoos and may have taken part in the family's wrongdoings.
The prosecution suspects that Song was deeply involved in irregular transactions involving the Yoos. In addition, Song is thought to have had a hand in purchasing photographs taken by Yoo for as much as 50 million won (S$60,000) each, dealing significant damage to Dapanda Co.
Song is the second of the seven to be questioned as a suspect in the unfolding case, following Chonghaejin Marine Co. CEO Kim Han-sik.
Kim, who was questioned on Tuesday, is thought to have aided Yoo in establishing massive slush funds and given him a monthly consultation fee of 15 million won.
Prosecutors are reported to be planning to seek arrest warrants for both Song and Kim later this week and also to question Yoo.
The Yoos are alleged to have received billions of won from companies they hold stakes in, including Chonghaejin Marine Co., for supposedly providing consultations.
The prosecution also suspects that Song managed stakes in various companies under borrowed names on behalf of Yoo.
Yoo and members of his family are suspected of a range of criminal activities including embezzlement, negligence, tax evasion and violating the foreign exchange act.
Chonghaejin Marine Co., owned by Yoo's sons through I-One-I Holdings, is suspected of keeping the ship in service despite being aware of structural faults and substandard safety features.
In addition, a shipping association official and two from Sewol's operator Chonghaejin Marine Co. were taken into custody on Wednesday on suspicion of corruption and negligence.
The two Chonghaejin officials are accused of failing to take action regarding the Sewol's inability to regain balance, which is thought to have been one of the major factors in the sinking of the ship.
The Sewol's usual captain, who was off duty on the day of the accident, has told the investigators that the ship had trouble maintaining balance. The captain, identified by the surname Shin, claimed that although he reported the issue to the company, no action was taken.
As the investigations close in on the Yoo family and the cause of the accident, the search for the Sewol's missing passengers continues two weeks after it sank off the coast of Jindo Island, South Jeolla Province.
Of the 476 passengers and crew on board the ship, 92 remain unaccounted for, with the death toll at 210.
More than 100 divers were deployed on Wednesday, with the search concentrating on the fourth and fifth decks. Spurring further controversy, a diving bell has yet to be deployed due to rapid currents.