Debbie Dunn, a sprinter who recently qualified for the United States Olympic track team, has removed herself from the team after a positive drug test at the Olympic trials.

Dunn’s urine sample at the trials showed that she had a banned synthetic testosterone in her system, according to a statement by Travis T. Tygart, the chief executive of the United States Anti-Doping Agency. A laboratory is testing a backup sample to see if it confirms the initial result.

“As in all cases, all athletes are innocent until and unless proven otherwise through the established full, fair legal process which was approved by athletes, the U.S. Olympic Committee and all Olympic sports organizations,” Tygart said.