The special investigation team on Monday raided homes and offices of those linked to the corruption and influence-peddling scandal surrounding President Park Geun-hye and her confidante, including Park's former right-hand man and incumbent culture minister.
The simultaneous raids -- led by independent counsel Park Young-soo -- targeted 10 places related to the scandal, with the home of former presidential chief-of-staff Kim Ki-choon being one of them.
Kim, 77, is suspected of condoning, or even protecting multiple illegal activities carried out by President Park's long-time friend Choi Soon-sil. Choi has been indicted for allegedly conspiring with Park and her former aides for crimes such as coercion, embezzlement and abuse of authority.
He had claimed repeatedly that he knew nothing of Choi, but recently admitted that he has had some knowledge of her.
The man, once referred to as the invisible hand behind the Park administration, is suspected of exercising undue influence over the Culture Ministry, as part of his effort to protect Choi's interests and muzzle complaints against the president.
Kim, recently barred from leaving the country, is suspected of ordering then-Vice Culture Minister Kim Hee-bum to have six high-ranking ministry officials resign from their posts in 2014.
Former Culture Minister Yoo Jin-ryong claimed that this was a prerequisite for establishing the Mir and K-Sports foundations, nonprofit organisations believed to have been founded as cover to channel public funds to Choi.
The disgraced top presidential aide is also embroiled in suspicion surrounding the so-called "blacklist" of those in culture circles who are anti-government.
Local civic groups filed a complaint to Park Young-soo's team earlier in the month against Kim, accusing him of instructing culture ministry officials to create the list and ban them from participating in state-funded projects.
The incumbent Culture Minister Cho Yun-sun's home and office were raided earlier in the day, along with ministry departments believed to have managed the list.
Kim Ki-choon is also accused of pressuring the culture ministry to appoint an acquaintance of former Vice Culture Minister Kim Chong as the vice chief of the organising committee for the 2018 PyongChang Winter Olympics.
Kim Chong was questioned by the special counsel team for the third straight day on Monday over the aforementioned allegation, along with the suspicion that he coerced local companies to provide financial support for organisations related to Choi and her family.
Investigators suspect that the contributions may have been in effect bribes to Choi -- who is linked to the president, with the biggest benefactor being Samsung Group.
Among those whose homes were raided Monday were former welfare minister Moon Hyung-pyo and Kim Jin-soo -- former Cheong Wa Dae senior secretary for health and welfare -- who are suspected of pressuring the National Pension Service to support a controversial merger of two Samsung Group companies in 2015.
"I think it would be fair to say that Moon is suspected of abusing his authority," said an official from the independent counsel's team.
The merger between Samsung C&T and Cheil Industries is believed to be crucial for Samsung Vice Chairman and heir apparent Lee Jay-yong to tighten his control over the entire Samsung Group.
Lee's family effectively "owns" the group via a complex cross-shareholding structure.
Hong Wan-sun, former head of the asset management division for the NPS, was also summoned Monday to be questioned by the special probe team on his role in the merger.
He denied to having received then-minister Moon's orders to support the move, but declined to answer any other questions.
In addition to Kim Ki-choon, another former Park aide Woo Byung-woo is also subject to investigation for allegedly knowingly condoning Choi's wrongdoings.
The prosecution's special team on Woo officially wrapped up their work and disbanded Monday, handing over the investigation files to the independent counsel's team.
In addition to charges of neglecting duty and abusing authority -- both related to Choi scandal -- Woo is accused of embezzling funds from a family-owned company, asserting influence for his son to receive favouritism during mandated military service, hiding personal assets via borrowed names and receiving kickbacks via a shady sale of his family's property in Seoul.
While Woo's Choi-related suspicions will be primarily handled by Park Young-soo's team, residual investigation on the former presidential secretary will jointly be conducted by the Seoul Central District Prosecutors' Office, according to officials.