A probe into financial irregularities at the Mohegan Tribal Gaming Authority’s Pennsylvania casino may have contributed to this week’s surprise resignation of the group’s CEO Bobby Soper.

On Tuesday, Soper abruptly announced that he was leaving the MTGA to “take on a new challenge.” Soper, who’d been CEO since 2015, declined to specify the nature of his new challenge, nor why he was leaving more than a year before his current MTGA contract expired.

On Wednesday, the MTGA filed papers with the US Securities and Exchange Commission (SEC) that referenced a review of “possible operational control deficiencies” at the group’s Mohegan Sun Pocono casino in Wilkes-Barre, Pennsylvania.

The filing notes that the Pennsylvania Gaming Control Board’s Office of Enforcement Control (OEC) had flagged the casino’s “system of tracking and reporting the issuance of certain customer incentives such as free slot play.”