South Korean lawmakers have begun an unprecedented series of hearings that will see the country’s business elite grilled over the current political scandal.

Heads of conglomerates such as Samsung and Hyundai will testify before a parliamentary investigation on Tuesday. The testimony comes ahead of an impeachment vote on Friday, which looks to remove President Park Geun-hye.

Samsung, the country’s largest business group, made the biggest contribution to the foundations of  Park’s confidante, Choi Soon-Sil. Companies such as Hyundai, SK, LG and Lotte are also involved.

Prosecutors have raided the headquarters of the groups for any evidence indicating that they received policy favors in exchange for donations.