CHAMPION steeplechaser Marta Dominguez was among the 14 people detained by the Spanish police on Thursday as part of an anti-doping operation.
Sportsmen, doctors, trainers, coaches and agents are being questioned on suspicions of crimes against public health.
In the 15 addresses raided in Madrid, Las Palmas, Alicante and Segovia the police found anabolic steroids, bags of blood, hormones and blood transfusion equipment.
Guardia Civil said Operation Greyhound began in April when they started tracking a group of people who were offering drug services to elite athletes.
Three of the people detained allegedly used sporting calendars to draw up doping plans for their sportsmen clients.
The athletes were treated with doping products such as anabolic steroids and transfusions of recycled blood, said the police.