The two have been in custody since last month. Cho, the country's first incumbent minister to be arrested while in office, resigned shortly after the court issued the arrest warrant. 

Both have also been charged with perjury for denying the allegations during a parliamentary hearing held last year. 

Former senior presidential secretary Kim Sang-yule and ex-presidential aide Kim So-young were indicted without detention on the same day for their alleged involvement with the blacklist.

The list is known to have nearly 10,000 people on it, including author Han Kang, winner of the Man Booker International Prize in 2016, and director Park Chan-wook, who won the grand prize at the Cannes Film Festival in 2004.

President Park has been mentioned in the indictment papers for her involvement in the alleged irregularities, the probe team's spokesman Lee Kyu-chul said during a regular press briefing. He declined to elaborate further.

Park, who is awaiting the Constitutional Court's decision on her impeachment, has flatly denied complicity.

The probe team and the presidential office Cheong Wa Dae are in talks over when and how to carry out a face-to-face questioning of Park, which would be the first interrogation of an incumbent South Korean president in a criminal case. 

Lee, the spokesman, said they expect the questioning to take place at around Friday.

Three other senior government officials, including former Culture Minister Kim Jong-deok, were indicted over similar charges last week. (Yonhap)