The former interpreter for Los Angeles Dodgers superstar Shohei Ohtani is facing federal charges related to his alleged theft of millions from the slugger, a source with direct knowledge of the investigation confirmed to ESPN late Wednesday.

The New York Times was first to report Wednesday that Ippei Mizuhara, 39, is in negotiations to plead guilty and that the investigation is racing toward a conclusion.

The probe started just three weeks ago when news broke that at least $4.5 million was transmitted from Ohtani's bank account to a California bookmaker under federal investigation.

In the first of a pair of interviews with ESPN, Mizuhara initially said he had amassed huge gambling debts and that Ohtani helped him out by wiring the money in $500,000 increments last year. But hours later, Mizuhara changed the account and said Ohtani had no knowledge of the payments.

Concurrently, attorneys for Ohtani alleged that he had been the victim of a "massive theft."

At a subsequent news conference, Ohtani told the media he never bet on baseball or any other sports, and had no knowledge of Mizuhara's alleged actions until a meeting after the Dodgers' season opener in Seoul, South Korea, during which Mizuhara addressed the team and said he had a gambling addiction. "I'm very sad and shocked that someone who I've trusted has done this," Ohtani said.

A source with direct knowledge of the investigation told ESPN late Wednesday that Ohtani's claims were accurate.

California attorney Michael G. Freedman confirmed to ESPN on Wednesday that he represents Mizuhara but declined to comment.

ESPN previously reported that Mizuhara is under investigation by the IRS, the Department of Homeland Security and the U.S. Attorney's Office for the Central District of California. Those agencies are also investigating Mathew Bowyer, the bookmaker Mizuhara said he paid, and are involved in a sprawling money laundering and illegal gambling case in Las Vegas.

The Times reported Wednesday that prosecutors have uncovered evidence that Mizuhara may have stolen more money from Ohtani than the $4.5 million initially reported. Mizuhara changed the settings on Ohtani's bank account so Ohtani would not receive alerts or confirmations about transactions, the Times also reported.

Mizuhara has not been seen publicly since returning to California from South Korea. The Times reported he was stopped by law enforcement officials after getting off the plane but was not arrested.

Information from ESPN's Tisha Thompson was used in this report.