The 50-game suspension indicates this is the second positive test in Singleton's career. He'll be allowed to participate in Spring Training, with the suspension starting at the beginning of the season.
Singleton, a left-handed-hitting first baseman who expected to start the season at Triple-A Oklahoma City, hit .284 with 21 homers and 79 RBIs in 131 games last year at Double-A Corpus Christi. The club acquired him from the Phillies in the Hunter Pence trade in 2011.
Singleton issued an apology Wednesday through his agents, Adam Karon and Matt Sosnick of Sosnick Cobbe Sports, that was obtained by ESPN.com
"I was informed today that I have tested positive for marijuana," Singleton said in the statement. "As a result, I am being suspended for the first 50 games of the 2013 season. I accept the penalty and take full responsibility for my actions. I apologize to my parents, the Houston Astros and [general manager] Jeff Luhnow.
"The Astros have been nothing but supportive of me and good to me in my short time with the organization. My hope is to use this as a learning experience and spend the rest of my career proving to myself and the baseball community that this was a lapse in judgment, and is not in any way indicative of my character or my dedication to baseball or to my team."
Luhnow issued a statement, as well:
"We learned today that Jonathan Singleton has tested positive for a drug of abuse and has been suspended 50 games as a result," he said. "We are disappointed in the decisions that Jonathan made leading up to this positive test. Jonathan has expressed regret for his decision and we expect will take the necessary steps to ensure this doesn't happen again. He has owned up to his actions and that is a necessary first step. The Astros will support Jonathan through this difficult time, and we hope this example will prevent other athletes from making similar decisions."