A U.S. Olympic hopeful in weightlifting tested positive for human growth hormone (HGH), becoming the first athlete found using the substance by the U.S. Anti-Doping Agency.

Pat Mendes, 21, a rising star in his sport and prospective medal favorite in the super heavyweight division at the London Olympics, confessed to using the drug after testing positive in two tests adminstered in February, the agency said in a statement.

Mendes, who graduated from Del Sol High in Las Vegas, accepted a two-year ban, which commenced March 19.

He becomes only the second U.S. athlete found using HGH. The first was minor-league baseball player Mike Jacobs, who tested positive under the program instituted by Major League Baseball last summer.

MLB began HGH testing during spring training this year, but no positives have been announced. Both the NFL and NBA added HGH testing to their new collective bargaining agreements, though neither has yet commenced testing.

No athletes tested positive for HGH in the first five years the test was administered, from 2004-2009, but more than a half dozen positive tests have been found in various international tests since.

“This case demonstrates yet again that the hGH test works to stop this dangerous drug from being used in sport,” USADA CEO Travis T. Tygart said in a statement. “We are pleased the athlete in this case chose to admit his use of hGH and accept the sanction.”