The Major League Baseball Players Association has taken an initial step toward unionizing the minor leagues, sending out authorization cards that will allow minor league players to vote for an election that could make them MLBPA members, union executive director Tony Clark told ESPN on Sunday night.

The potential unionization of more than 5,000 minor leaguers is the latest action in an extended effort by players who won a $185 million settlement from the league in an unpaid wages class-action lawsuit and have received housing from teams and increased pay in recent years.

Minor league players, whose compensation and benefits are not collectively bargained, continue to argue for higher salaries.