Tyson Gay tests positive for banned substance

American 100-meter record-holder Tyson Gay will pull out of the world championships next month in Moscow after admitting to testing positive for a banned substance.

The U.S. Anti-Doping Agency informed Gay Friday that a sample from an out-of- competition test on May 16 came back positive. Gay did not reveal the substance.

The "B" sample will be tested soon.

The 30-year-old Gay won the 100- and 200-meters at nationals in June.