The Mexican Football Federation has cleared the five international players who tested positive for the banned substance clenbuterol and announced they will not face further punishment.
Mexico suspended five members of their Gold Cup squad - Antonio Naelson, Christian Bermudez, Edgar Duenas, Francisco Rodriguez and Guillermo Ochoa - after they all failed a test at a pre-tournament training camp in May.
The disciplinary committee of the Mexican Football Federation launched an investigation into the positive tests, but announced on Friday that the adverse results were due to 'food contamination'.
A statement on the federation's official website said: "The players took all necessary precautions to avoid ingestion or consumption of the prohibited substance.
"According to Article 47 paragraph 2 of the Fifa Anti-Doping Regulations, the players explained how the prohibited substance entered his body and there was no culpable or negligent conduct on his part in the ingestion of that substance.
"There should be no application of a period of suspension."
The statement added that Fifa and WADA - the World Anti-doping Agency - would be informed of the findings.