South Korea's National Assembly is set to hold a second round of hearings to investigate a corruption scandal involving President Park Geun-hye on Wednesday.

Park's former key aides including an ex-chief of staff will testify during the session likely to focus on suspicions that her confidante Choi Soon-sil and her associates meddled in government affairs. But Choi and some key suspects in the scandal will not attend.

On Tuesday, the parliamentary committee grilled the heads of eight conglomerates on their alleged connections to Choi. They were found to have donated to two nonprofit foundations controlled by Choi. She is suspected of embezzling money from them. 

The business tycoons denied allegations that they were seeking favors in exchange for their contributions, claiming they could not turn down donation requests from the presidential office.

Choi was arrested last month on charges of abuse of power, coercion and fraud. Prosecutors said Park was also an accomplice.

The focus of Wednesday's hearing is expected to be on Kim Ki-choon, former presidential chief of staff, who exerted immense influence in the Park administration. 

Choi and her family and close associates told the panel they will not attend citing health reasons. The whereabouts of Choi's daughter Chung Yoo-ra and Woo Byung-woo, ex-senior presidential secretary for civil affairs, remain unknown.

The National Assembly said it may issue an order to have the key figures attend the session forcibly.  (Yonhap)