SEOUL (Reuters) - South Korean prosecutors questioned the chairman of the SK Group on Saturday in connection with an influence-peddling scandal that brought down President Park Geun-hye, the latest corporate leader to come under suspicion.

Park, South Korea’s first democratically elected leader to be removed from office, faces allegations that she colluded with a friend, Choi Soon-sil, to pressure big businesses to donate to foundations set up to back her policy initiatives.

Officials at the prosecutors’ office could not be reached immediately for comment about their reasons for summoning SK Chairman Chey Tae-won.

Chey did not comment to reporters when he arrived at the prosecution office. A spokesman for the SK Group also declined to comment.

Park is due to appear for questioning on Tuesday.

She and Choi have denied wrongdoing.

An election to pick a new president will be held on May 9 and reform of South Korea’s powerful family-run conglomerates, known as chaebol, is a major campaign issue.

The SK Group is South Korea’s third-largest chaebol, with units in chemicals, telecoms and semiconductors.

Chey is likely to be asked about discussions between the group and the presidential Blue House in 2015, around the time he was released from prison when a four-year term for embezzlement was commuted.

Three SK executives were questioned on Thursday as part of the same investigation.

At least two other conglomerates are being investigated, including the Samsung Group, South Korea’s largest chaebol. Its leader, Jay Y. Lee, is in detention on trial on bribery, embezzlement and other charges.

Lee denies all charges and Samsung denies wrongdoing.

A spokesman for the Lotte Group said this week it was cooperating with the prosecutors’ investigation.

Park, who was impeached by parliament in December and dismissed from office by the Constitutional Court on March 10, is accused of bribery, extortion and abuse of power in the scandal that has rocked South Korea since October.

The political crisis comes as tension with North Korea has been rising over its weapons development in defiance of U.N. resolutions.

U.S. Secretary of State Rex Tillerson said in Seoul on Friday a military response would be “on the table” if North Korea took action to threaten South Korean and U.S. forces.

Tillerson also dismissed Chinese opposition to South Korea’s deployment of an advanced U.S. anti-missile system aimed at defending against North Korea. China says the system’s powerful radar is a threat to its security.

Tillerson was in China on Saturday for what is likely to be a prickly visit, with China angry about being told to do more to rein in North Korea.