Tests conducted at the Spanish athletics championships in July returned three "adverse analytical findings", the head of the country's anti-doping agency (AEPSAD) told the lower house of parliament on Thursday.
AEPSAD president Ana Munoz did not reveal the names of the athletes but said their licences have been suspended while the correct procedures are followed.
Two of the substances detected carry lengthy bans according to World Anti-Doping Agency (WADA) rules and the positive results have been confirmed by the WADA-accredited laboratory in Lausanne, Switzerland, she added.
The tests were the first conducted by AEPSAD since it was granted wider powers in new anti-doping legislation.
The law was part of Spain's effort to dispel a perception it is soft on doping, seen as one reason for the failure last week of Madrid's bid for the right to host the 2020 Olympic Games.
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