Outfielder Marlon Byrd, who admitted to working with the man whose center triggered a federal investigation of steroids use and distribution among athletes, has tested positive for performance-enhancing drugs.

The league announced on Monday that the free agent has received a 50-game suspension after testing positive for Tamoxifen. He will be put on the restricted list and will remain there until Aug. 20.

Tamoxifen -- its brand name in the United States is Nolvadex -- is a medicine that blocks the effects of the estrogen hormone in the body. It is used to treat breast cancer in women or men and is used by steroid users to prevent the growth of breast tissues in men and to stop post-cycle crashes.

Byrd issued a statement through the Major League Baseball Players Association Monday.

"I made an inexcusable mistake," the statement said. "Several years ago, I had surgery for a condition that was private and unrelated to baseball. Last winter, I suffered a recurrence of that condition and I was provided with a medication that resulted in my positive test. Although that medication is on the banned list, I absolutely did not use it for performance-enhancement reasons.