The Vice Chairman of Samsung Group, Lee Jae-yong, on Thursday morning arrived at the prosecutor's office for questioning in a bribery case, media reports said.
Lee, is the heir apparent of South Korea's largest family-run conglomerate that was being investigated for the scandal involving impeached South Korean President Park Geun-hye, Xinhua news agency reported.
Lee was seen on TV footage telling reporters that he felt "very sorry" and apologised to the people for the matter before entering the independent counsel's office.
He would be questioned as a suspect in the influence-peddling scandal.
Samsung was suspected of having provided the biggest donations among scores of conglomerates to two non-profit foundations controlled by Choi Soon-sil, Park's long-time confidante at the centre of the scandal.
Samsung also signed a $18.6 million contract with a German company, owned by Choi and her daughter, to provide financial assistance for the daughter's equestrian training.
The company also offered billions of dollars to a winter sports centre managed by Choi's niece.
Suspicion was raised that the financial assistance was provided in return for getting support in the merger in July 2015 of two Samsung affiliates to create a de facto holding company.
The merger between Samsung C&T, a construction unit, and Cheil Industries, a former de facto holding company, was extremely crucial to the management control transfer to the vice chairman from his father Chairman Lee Kun-hee who has been hospitalised for heart attack since May 2014.
President Park and Vice Chairman Lee met face-to-face around the time of the merger.
If any quid pro quo deals are proven between Lee and Park or between Lee and Choi, convicts could be sentenced to the maximum of life in jail.