Three-time Tour de France winner Alberto Contador was cleared of doping charges Tuesday after the Spanish cycling federation decided he should not be banned for testing positive for clenbuterol.

A minute trace of the muscle-building and fat-burning drug, used illicitly to produce leaner meat more quickly in livestock, was found in Contador’s urine sample after the Tour de France last July.

Contador said he had not ingested clenbuterol to improve his athletic performance, but had unknowingly eaten meat containing the substance.

His case has highlighted concerns that clenbuterol might be consumed unwittingly by eating meat from animals who were fed the drug.  Clenbuterol is not licensed for any use in the United States and while some countries permit the limited use of the drug in animals not meant for food, only a few countries have approved small doses of it for therapeutic uses in food producing animals.

The drug can pose problems to human health, such as heart palpitations, muscle tremors, nervousness, dizziness, nausea, vomiting, fever, chills and, in rare cases, death. It is increasingly bought and sold under the table for use in livestock feed to provide the same  effects it does for athletes — accelerated fat burning and muscle growth. 

Cycling’s governing body, the UCI, and the World Anti-Doping Agency (Wada) have the right to appeal the Spanish cycling federation’s decision.