The French newspaper Le Monde has reported the laboratory that tested American cyclist Floyd Landis's urine samples during the Tour de France has admitted to making an administrative error on his back-up "B" sample.

In its Wednesday edition, the newspaper said the Chatenay-Malabry lab outside of Paris mislabeled Landis's second sample, putting an incorrect number on it. Tests on the rider's two samples showed elevated levels of testosterone when he won cycling's premier race in July.

Landis's attorney, Howard Jacobs, has already alleged that the French lab made repeated errors analyzing the samples, including mismatched sample code numbers. On Sunday, Landis again denied taking testosterone and said the lab made crucial errors in his tests.

Race organizers no longer consider Landis the 2006 Tour champion. But the admission of the error is expected to boost Landis's appeal against the positive result at his arbitration hearing Friday in the United States. If found guilty of doping, Landis will be formally stripped of the title and banned for two years.