3/22 -- 3:18 PM PT -- MLB just announced it has officially launched its probe into the matter ... saying, "Major League Baseball has been gathering information since we learned about the allegations involving Shohei Ohtani and Ippei Mizuhari from the news media."

"Earlier today, our DOI began their formal process investigating the matter."

MLB is doing its due diligence with Shohei Ohtani ... with sources telling TMZ Sports that league officials are gathering information to determine if the face of baseball was involved in the gambling scandal surrounding his translator.

Ohtani's inteprator and best friend Ippei Mizuhara has given conflicting stories on Shohei's involvement ... first saying the Dodgers superstar was well aware of his huge gambling debts, and loaned him millions of dollars to get out of the hole. He later backtracked, saying the Japanese two-way athlete had no idea.

As for Ohtani, his attorney claims he's been the victim of a "massive theft."

Now, MLB's trying to figure out what the hell is going on -- not necessarily because they believe Shohei did anything wrong -- but because gambling is an existential threat to any pro sport.

Look no further than Pete Rose ... who despite his exploits on the diamond, was banned for life in 1989 after he admitted to wagering on games -- although no one has accused Ohtani of betting on baseball, or any other sport for that matter.

It's worth noting, it sounds like Ohtani -- who signed a 10-year, $700 million contract with the Dodgers this offseason -- has nothing to hide.

We're told his team alerted authorities to the "theft" ... and the feds are currently investigating.

No one connected to the probe has been arrested.

The Dodgers are 1-1 on the season, and their newly signed star is off to a solid start, despite the scandal ... collecting 3 hits and 2 RBIs in 10 plate appearances on the season.