SK Group Chairman Chey Tae-won will attend a Fair Trade Commission session next month involving SK Siltron, the antitrust body said Wednesday. The antitrust watchdog has been looking into SK Group’s 2017 buyout of LG Siltron for the past four years, following suspicions that the SK Group chairman’s personal purchase of a stake in the firm violated the law.

In January 2017, the conglomerate acquired a 51 percent stake in LG’s silicon wafers manufacturing unit, now named SK Siltron. In April that year, SK additionally purchased a 19.6 percent stake while Chey personally bought another 29.4 percent stake. The watchdog has recently notified SK Group of its intention to refer the case to the prosecution.

According to the FTC, Chey has expressed his willingness to explain the case in person to the nine FTC commissioners, and the watchdog rescheduled a full-member session set for Dec. 8 to Dec. 15 to allow for Chey’s attendance.

It is unusual for the head of a company to attend a meeting in person as the watchdog does not require the person involved to be present.

Chey and SK Group deny any wrongdoing, saying the tycoon acquired the shares via an open auction and spent his own money in order to protect the local semiconductor market as overseas investors had moved to buy the stake.