AIGLE, Switzerland, July 26 (AP)  An unidentified cyclist tested positive for doping during the Tour de France, potentially widening the scandal that gripped this year’s race before it even began.

The rider’s name, team and nationality will not be released until the testing process is completed, including the analysis of a backup sample, the International Cycling Union said Wednesday.

The U.C.I., the sport’s governing body, said the rider’s team and national federation were notified, as well as national and world antidoping authorities. USA Cycling had not been contacted by U.C.I., according to the organization’s spokesman, Andy Lee. A spokeswoman for the United States Anti-Doping Agency said that group had no comment.

The American cyclist Floyd Landis won the Tour de France on Sunday, keeping the title in United States hands for the eighth straight year. Lance Armstrong, long dogged by doping whispers and reports that he has vehemently denied, won the previous seven.