Jan Ullrich's blood samples won't be turned over to Spanish police investigating a doping scandal, the president of the world cycling body said Wednesday.

Ullrich, the 1997 Tour de France winner, was among the top riders implicated in May when police arrested five people at a Madrid clinic after seizing drugs and frozen blood.

The UCI samples could be used for a DNA comparison with the frozen blood found in the raid. Police suspect the samples were to be prepared for performance-enhancing transfusions to still-unidentified riders.

"The blood of the riders in our possession from doping controls is used for research purposes," UCI president Pat McQuaid said. "To give it for DNA comparisons is against our rules."

Ullrich and Ivan Basso were among the riders excluded from the Tour de France because of alleged links to the doping scandal.