NEW YORK (Reuters) - San Francisco Giants catcher Eliezer Alfonzo has been suspended for 50 games for testing positive for a performance enhancing drug, Major League Baseball said on Wednesday.

Alfonzo is a member of the club's 40-man roster but is currently with Triple-A team Fresno.

The pitcher's suspension will begin on Thursday, the league said in a statement.

"The Giants were disappointed to learn that one of our players, Eliezer Alfonzo, has failed a test for a performance enhancing drug. Our organization fully supports Major League Baseball's Joint Drug Prevention and Treatment Program," the Giants said in a statement.

"As an organization, we will continue to work with our players, Major League Baseball and the Players Association to do what we can do to eliminate these performance enhancing substances from our game," they added.

No details were given of the nature of the drug.

(Reporting by Simon Evans in Miami; editing by Trevor Huggins)