Four followers of ex-Semo Group chief Yoo Byung-eon were detained over the weekend on suspicion of helping the de facto owner of the sunken ferry Sewol to flee.
The Incheon District Prosecutors' Office said Sunday that it was questioning four members of the Salvation Sect, which is allegedly led by Yoo. Prosecutors think they are part of a group of key devotees of the sect who reportedly orchestrated Yoo's getaway.
The prosecution verified their identities by reviewing CCTV footage seized during a raid on Geumsuwon, a religious compound run by the sect in Anseong, Gyeonggi Province, Wednesday.
After the prosecution failed to capture the reported leaders of the sect in the raid, it warned that any person hiding Yoo or his oldest son Dae-gyun would be subject to stern punishment.
Further, investigative authorities on Sunday drastically increased the reward level up to 500 million won (S$610,000) for Yoo and 100 million won for his son, up from 50 million won and 30 million won, respectively.
The prosecution also said it has obtained intelligence that Yoo recently stayed at a follower's residence in Suncheon, South Jeolla Province.
Meanwhile, about 10 followers of Yoo protested the arrest of the suspect by visiting the Incheon District Prosecutors' Office in Hagik-dong.
Investigators are reportedly hoping that some of Yoo's devotees may become whistle-blowers.
Last Thursday, the Incheon District Court approved the arrest warrant for the former Semo Group chief.
The warrant expires July 22, while an ordinary warrant matures one week after it is issued.