Five Mexican internationals, currently taking part in the Gold Cup tournament in the United States, were on Thursday suspended for doping, the secretary general of the country's football federation (Femexfut) announced.
The five were named as goalkeeper Guillermo Ochoa, who plays for the America club in Mexico, defenders Francisco Javier Rodriguez, of Dutch side PSV, and Edgar Duenas of Toluca in Mexico.
Midfielders Antonio Naelson, of Toluca, and Atlanta's Christian Bermudez are the other two players.
"From now we'll go through a very difficult period which will see the players separated and an inquiry opened. It's an unpleasant and difficult moment but we have to respect the rules," said Femexfut secretary general Decio de Maria.
The federation refused to divulge the substances involved or when the drugs tests took place.
Mexico are due to play Cuba later Thursday in Charlotte, North Carolina, in their latest Gold Cup match.
They defeated El Salvador 5-0 in their opening fixture on Sunday.