Former President Park Geun-hye faces allegations of bribery, abuse of power, coercion and leak of government secrets in 13 difference cases involving her close friend and former aides.
Park, Korea's first leader to be ousted by impeachment, is scheduled to appear at the Seoul Central District Prosecutors' Office in southern Seoul on Tuesday morning to undergo questioning.
She is suspected of colluding with her friend Choi Soon-sil and former aide An Chong-bum in pressuring local conglomerates to donate some 77.4 billion won (US$69 million) to two dubious foundations -- Mir and K-Sports -- allegedly controlled by Choi.
State prosecutors accused Park of abuse of power and coercion and an independent counsel later concluded that such an act constitutes bribery.
After a monthslong investigation, the independent counsel team indicted Lee Jae-yong, the de facto leader of Samsung Group, on charges of bribing Choi, and in effect Park, in return for business favors.
Special investigators viewed the 20.4 billion won the business group donated to the two foundations, as well as its other business transactions with Choi's company, as kickbacks.
The state prosecutors are now expanding their probe into other conglomerates.
SK Group Chairman Chey Tae-won was grilled by prosecutors on Saturday over suspicions the conglomerate donated a total of 11.1 billion won to the foundations in return for a presidential pardon for him. Chey was then serving a prison term for embezzlement and other charges.
A senior prosecution official earlier said they will decide whether such collection of money can be deemed as coercion or bribery after getting the facts straight based on Park's questioning.
The former president has also been named an accomplice in blacklisting cultural figures deemed critical of her administration to deny them state support.
Former Culture Minister Cho Yoon-sun and Park's ex-chief of staff Kim Ki-choon are standing trial for allegedly orchestrating the creation and management of the list, which is known to have over 9,000 people's name on it.
Another former presidential aide Jeong Ho-seong is standing trial on charges of leaking government documents, including confidential information, to Choi under the direction of Park. There have been allegations Choi, who held no official government post nor has any policy experience, peddled influence in key state affairs using her ties to the former president.
Prosecutors also accuse Park of abusing her authority to fire government officials who were not supportive of such alleged irregularities carried out in the past years and peddling influence to give business favors to those close to Choi.
Park has flatly denied all suspicions against her Park and has so far rejected a direct investigation, as the Constitution stipulates that an incumbent president has immunity from prosecution. The Constitutional Court stripped her of that privilege on March 10. (Yonhap)