Prosecutors planned to question a former vice culture minister on Sunday over suspicions he received more than 1 billion won ($847,000) in bribes from a local businessman.
The move came weeks after SLS Group Chairman Lee Kuk-chul claimed he gave the money to former Vice Culture Minister Shin Jae-min over the past decade.
The businessman, who built the conglomerate that focuses on shipbuilding and heavy industries, also made a separate claim he gave a total of about 50 million won in gift certificates to at least two presidential officials via Shin in 2008 and 2009.
The businessman has claimed he came forward with the revelations because he has been unfairly investigated over and over again in what he said was a plot to topple his conglomerate.
A series of SLS subsidiaries have either gone bankrupt or into a debt workout program since 2009 when the chairman was investigated on suspicion of bribery and other charges. In November last year, he was sentenced to three years in prison, which was suspended for five years.
Shin and other officials have rejected Lee's claims.
On Sunday, Shin accepted responsibility for his actions in a social media posting. "I will accept (punishment) if what I did is a crime," Shin wrote in a comment on his Facebook page before reporting to answer the prosecutors' summons.
Prosecutors plan to question Shin over whether the SLS chairman asked Shin to exert influence over SLS subsidiaries, a source said.
The investigation comes more than a week after prosecutors arrested Kim Du-woo, a former senior presidential aide, over a separate bribery case involving a suspended savings bank.
The latest probe also comes more than a week after President Lee Myung-bak called for stern handling of alleged bribery cases involving some of his close aides.
Previous governments were plagued heavily by corruption cases in their final years in office. Lee's predecessor, Roh Moo-hyun, committed suicide in 2009 amid a prosecution investigation into irregularities involving his relatives. (Yonhap)