PAU, France (Reuters) - Luxembourg rider Frank Schleck has denied any wrongdoing after he was withdrawn from the Tour de France on Tuesday when he returned a positive test for the diuretic Xipamide following Saturday's Stage 13.

"I categorically deny taking any banned substance. I have no explanation for the test result and therefore insist that the B sample be tested which is my right," Schleck said in a statement sent to Luxembourg media network RTL overnight

"If this analysis confirms the initial result, I will argue that I have been the victim of poisoning," added Schleck, who was in 12th place in the overall standings.

Schleck, who finished third last year, was pulled out of the race by his RadioShack team immediately after the test result was announced.

He is not suspended because according to the World Anti-Doping Agency (WADA), Xipamide was "a specified substance", which allowed for a greater reduction of a two-year sanction when an athlete tested positive for it.

(Reporting by Julien Pretot; Editing by John O'Brien)