Former Spanish mountain bike rider Alberto Leon, 37, has been found dead after being implicated in two major doping scandals, police sources said in the night to Tuesday, DPA reported.
Initial evidence pointed to a suicide, the sources said.
The daily El Pais said Leon had hung himself at his home in San Lorenzo de El Escorial near Madrid, where his body was discovered on Monday.
Leon was implicated in the 2006 Operation Puerto, which targeted cyclists, team officials and doctors over blood doping.
Famous riders such as former Tour champ Jan Ullrich were sacked by their teams, while Alejandro Valverde and Ivan Basso served competition bans. However, the legislation in force at the time did not allow for Leon and other suspects to be punished.
In late 2010, Leon was implicated in the Operation Galgo (Greyhound) alongside 13 other people including world steeplechase champion Marta Dominguez.
The 14 were suspected of involvement with a ring which supplied athletes with banned substances.
Leon, who was one of the Spanish mountain bike pioneers, was not believed to have taken doping substances himself. He was thought to have acted as a helper to Eufemiano Fuentes, a sports doctor implicated in both doping scandals, press reports said.
Leon was suspected of acts such as transporting doping substances and performing blood transfusions, according to El Pais.