An investigation into Major League Baseball’s pipeline of young talent from the Dominican Republic has documented a system in which teenage prospects are recruited, trained and sometimes discarded with limited oversight or protection, raising longstanding concerns about labor practices in the sport’s international talent development.

The investigation details how academies run by MLB franchises or their affiliates recruit boys as young as early teenagers, some of whom leave school to pursue a shot at professional baseball, with only a small fraction ever reaching the majors.

MLB has previously defended its international development system as providing opportunity that would not otherwise exist for many Dominican families, while acknowledging room for improved player protections.