The former interpreter for Shohei Ohtani stole more than $16 million over two years from the Los Angeles Dodgers superstar to pay off gambling debts to an illegal sportsbook, according to an affidavit filed by federal authorities Thursday.

Federal authorities filed a complaint accusing Ippei Mizuhara, 39, of bank fraud, which can carry a maximum fine of up to $1 million and/or up to 30 years in prison, according to federal sentencing guidelines.

"I want to emphasize this point: Mr. Ohtani is considered a victim in this case," U.S. Attorney Martin Estrada said during a news conference in Los Angeles.

Estrada added there was no evidence Ohtani had any knowledge of Mizuhara's gambling activities or use of his bank account to pay his debts. He said investigators combed through years of text messages between the two and found no discussion of gambling.

"Mr. Mizuhara used and abused that position of trust ... in order to plunder Mr. Ohtani's bank account to the tune of over $16 million," Estrada said.

Mizuhara is expected to appear in U.S. District Court on Friday afternoon, during which an arraignment date will be set, according to a spokesperson for the U.S. Attorney's Office. Mizuhara's lawyer, Michael G. Freedman, declined to comment.

IRS special agent Tyler Hatcher told ESPN that the agencies have interviewed Mizuhara "at least twice."

Ohtani, referred to in the complaint only as a "professional baseball player," told authorities that he did not authorize the transfers.

A spokesperson for Ohtani declined to comment.

"Given the information disclosed today, and other information we have already collected, we will wait until resolution of the criminal proceeding to determine whether further investigation is warranted," MLB said in a statement.

In 2018, the year Ohtani moved to the United States, Mizuhara helped him open a bank account where his Angels salary was deposited, the complaint states. Ohtani said he never gave Mizuhara control of his accounts, but Mizuhara allegedly told Ohtani's financial advisers and accountants, none of whom spoke Japanese, that Ohtani had denied them access to the account, according to the affidavit.

Text messages showed that Mizuhara began gambling with a bookmaker in September 2021 and began losing "substantial sums of money" later that year. In all, the complaint states, Mizuhara averaged 25 bets per day, ranging from $10 to $160,000 per bet, between December 2021 and this January -- some 19,000 bets in all. Mizuhara's betting records, according to a spreadsheet obtained by authorities, reflected total winnings of $142 million and total losses of $183 million during this span, "leaving a total net balance of negative $40,678,436."

While the bookmaker is not named in the complaint, his role and detail match that of Mathew Bowyer. Bank records also show that the phone number and email address on Ohtani's account were changed to those associated with Mizuhara in late 2021. Prosecutors said that winnings were deposited in Mizuhara's account, not Ohtani's.

Bowyer's attorney, Diane Bass, declined to comment. The Dodgers, who fired Mizuhara on March 20, also declined to comment.

According to the affidavit, Mizuhara repeatedly texted the bookmaker asking for more credit. On Nov. 14, 2022, he wrote, "I'm terrible at this sport betting thing huh? Lol . . . Any chance u can bump me again?? As you know, you don't have to worry about me not paying!!"

Investigators also relied on recorded phone calls from the bank in which Mizuhara falsely identified himself as Ohtani to "trick and deceive" bank employees into authorizing the transfers. The complaint outlined one specific transfer on June 20, 2023, of $500,000 to an associate of a bookmaker.

Text messages from the filing show that around November 2023, the relationship between Mizuhara and the bookmaker changed. On Nov. 17, the bookmaker texted: "I don't know why you're not returning my calls. I'm here in Newport Beach and I see [Ohtani] walking his dog. I'm just gonna go up and talk to him and ask how I can get in touch with you since you're not responding? Please call me back immediately."

There's no indication in the complaint that anyone connected with the bookmaker ever made contact with Ohtani. Bass has said Bowyer had no contact with Ohtani.

On March 20, 2024, after news broke that at least $4.5 million was transmitted from Ohtani's account to Bowyer's operation, Mizuhara texted the bookmaker asking if he'd seen the media reports. The bookmaker replied, "Yes, but that's all bulls---. Obviously you didn't steal from him. I understand it's a cover job I totally get it."

Mizuhara replied, "Technically I did steal from him. It's all over for me."

Authorities said Mizuhara never bet on baseball, which Mizuhara previously told ESPN.

When asked why the investigation, which started three weeks ago, took place so quickly, Estrada said: "We understood there was significant amount of public interest in this case."

In the first of a pair of interviews with ESPN, Mizuhara 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."

Authorities said they did not believe Ohtani had wired the money, as Mizuhara claimed in his first interview with ESPN. They said Ohtani first learned that Mizuhara had accessed his accounts during a team meeting after the Dodgers' season opener in Seoul, South Korea, during which Mizuhara addressed the team and said he had a gambling addiction. Ohtani previously gave the media a similar account during a news conference on March 25, five days after his attorneys made the allegation of theft.

The affidavit further details the agencies' work on the larger investigation of illegal sports bookmaking organizations in Southern California and money laundering through casinos in Las Vegas. That investigation has so far led to criminal charges or convictions against 12 people, including former minor league baseball player Wayne Nix. Nix was also a Southern California bookmaker whose clients included NBA legend Scottie Pippen, former MLB All-Star Yasiel Puig and Maverick Carter, the longtime manager and friend of LeBron James.

The filing also outlines the agencies' investigation of Bowyer, whose phone and residence were searched in October 2023. In a group text, a casino employee introduced Bowyer to a potential bettor, saying that Bowyer "takes big action and can give you whatever u need."

Until he was fired, Mizuhara had interpreted for Ohtani since 2018, accompanying the two-way player in dugouts, locker rooms, player lounges, on trips, in media settings and elsewhere, making Mizuhara highly recognizable to baseball fans. The two were rarely separated. The filing describes Mizuhara as Ohtani's "de facto manager."

ESPN's Tisha Thompson and T.J. Quinn contributed to this report.