Major League Baseball says it has opened an official investigation into alleged illegal gambling involving Japanese MLB star Ohtani Shohei and his interpreter, Mizuhara Ippei.

In a statement released on Friday, the operator of the top US baseball league said it has been gathering information since it learned about the allegations involving the two from the news media. MLB said its "Department of Investigations began their formal process investigating the matter."

The move follows US media reports that Mizuhara was found engaging in illegal gambling and that he was fired by the Los Angeles Dodgers, who employed him to interpret for Ohtani.

The US sports channel ESPN has reported that about 4.5 million dollars was transferred from Ohtani's bank account to an alleged illegal bookmaker.

ESPN says during an interview with Mizuhara, the interpreter initially said he asked Ohtani to help him pay off his debts, which had reportedly snowballed from gambling. But Mizuhara later retracted the statement. ESPN says Ohtani only became aware of the gambling issues involving him after Wednesday's season opener.

US tax authorities are investigating Mizuhara and the alleged illegal bookmaker.

ESPN says Ohtani's lawyers have asked the authorities for investigation and claimed their client had been the victim of a "massive theft."