Major League Baseball is investigating multiple clinics in South Florida, armed with the belief that the region stretching 50 miles south from Boca Raton to Miami is "ground zero" for performance-enhancing drugs.

ESPN's "Outside the Lines" has learned that Major League security officials have spent considerable time in South Florida since the summer of 2012, monitoring clinics believed to be linked to the sale of human growth hormone and testosterone to players.

One clinic under investigation is operated by Anthony Bosch, a self-described biochemist who most recently ran Biogenesis of America in Coral Gables.

The New York Daily News on Saturday first reported that MLB is investigating Bosch, whom the newspaper said had been an adviser to Yankees third baseman Alex Rodriguez.