Hamburg - German rider Stefan Schumacher tested positive twice for third-generation EPO at the Tour de France in July, the French anti-doping agency AFLD announced on Wednesday.

The AFLD said in a statement that Schumacher tested positive for the newest version of the blood-booster, CERA (Continuous Erythropoiesis Receptor Activator), on July 3 and July 15.

The AFLD said that it has informed the ruling cycling body UCI, the World Anti-Doping Agency (WADA) and Germany's anti-doping agency NADA about the findings in retests of the samples gathered at the race.

Retests at the French laboratory in Chatenay-Malabry were conducted on riders who returned abnormally high blood readings during the Tour.

Italian riders Leonardo Piepoli and Riccardo Ricci also tested positive for CERA at the Tour and other riders may also be caught by a new test method.

Schumacher won both individual time trials at the Tour and was the overall leader of the race for two days.

Schumacher, who is yet to comment on the positive tests, faces a two-year ban if found guilty of doping. The German cycling federation BDR and NADA have launched investigations, with the BDR on Monday giving Schumacher a five-day deadline to explain himself.

He has been suspended by his Gerolsteiner team.