The Los Angeles Dodgers said Thursday they had fired Shohei Ohtani's interpreter after the Japanese baseball star's representatives claimed he had been the victim of "a massive theft" reported to involve millions of dollars.

Ippei Mizuhara is alleged to have stolen money from the Japanese ace to place bets with a suspected illegal bookmaker.

The Los Angeles Times reported that West Hollywood law firm Berk Brettler LLP had looked into Mizuhara's actions after the newspaper learned that Ohtani's name had surfaced in a federal investigation of alleged illegal bookmaker Mathew Bowyer.

"In the course of responding to recent media inquiries, we discovered that Shohei has been the victim of a massive theft and we are turning the matter over to the authorities," Berk Brettler said in a statement.

The LA Times, citing two anonymous sources, said the money involved "was in the millions of dollars" and Mizuhara used it to place bets with Bowyer's operation.

ESPN reported questions had arisen around "at least $4.5 million in wire transfers sent from Ohtani's bank account" to an associate of Bowyer.

ESPN said that multiple sources, including Mizuhara himself, told ESPN that Ohtani doesn't gamble and that the funds covered Mizuhara's losses.

Major League Baseball's gambling policy bars "any player, umpire, or Club or League official or employee" from betting on baseball or making illegal bets on any other sport.

While sports betting has been legalized in a majority of US states, online betting and retail sports books remain illegal in California.

Mizuhara, who was born in Japan but was brought up in Southern California, became Ohtani's personal interpreter when he signed with the Angels in 2017 and followed him to the Dodgers.

He has been a close companion of Ohtani, who has emerged as the global face of MLB. (AFP)