Erica Watts, 24, am open water swimmer from Indiana who finished second at the last US championships has accepted a two-year suspension for what is said to have been an "inadvertent" violation of anti-doping rules, according to the the US Anti-Doping Agency.

The swimmer, from Carmel, Ind., tested positive for methylphenidate, or Ritalin, at the championship meet on June 2 in Fort Myers, Florida. She had disclosed her use of a prescription medication containing the substance at the time of the test, but she did not have a medical exemption in place before the competition, the agency said.

The rules require such documentation before a competition to confirm a valid medical need for using prescription drugs. Athletes may receive exemptions if proper documentation is in place, the agency said.

Watts can return to competition July 13, 2007. she has been stripped of her second -place finish at the US championships.