Major League Baseball has opened a formal investigation into the matter surrounding Los Angeles Dodgers superstar Shohei Ohtani and his former interpreter, Ippei Mizuhara, the league announced Friday.

MLB is expected to request interviews with all parties, including Ohtani and Mizuhara, a source told ESPN, although officials will have no way to compel Mizuhara’s cooperation since he no longer works in baseball.

Ohtani also has a right to refuse cooperation as a member of the MLB Players Association. Ohtani could invoke his right, under an interpretation of arbitration precedent, to refuse cooperation because of a criminal investigation that’s already underway. Traditionally, MLB has argued a player can invoke such an exception if he is a target of the investigation, which Ohtani is not believed to be.

MLB said in a statement that it began gathering information about the allegations involving Ohtani and Mizuhara after reports came out this week. Its department of investigations began formally investigating the matter Friday, the league said.