Five players in Mexico's squad at the Concacaf Gold Cup in the United States have tested positive for the banned substance clenbuterol, the general secretary of the Mexican Football Federation (Femexfut) Decio de Maria said on Thursday.
De Maria named the players as goalkeeper Guillermo Ochoa, defenders Francisco Rodriguez and Edgar Duenas and midfielders Antonio Naelson 'Sinha' and Christian Bermudez and said they had all been suspended from the tournament.
He added that any further sanctions, which could include bans of up to two years, would be determined by Femexfut.
"Last night we received the anti-doping analysis of 14 players of the 'Tri' (national team) that were done on May 21 and five players showed positive," De Maria told a news conference.
"The substance for which they were positive is Clenbuterol. The players will be withdrawn from (coach) Jose Manuel de la Torre's team."
Title holders Mexico were due to play Cuba in their second Gold Cup Group A match in Charlotte later on Thursday. They beat El Salvador 5-0 in their opener.
De Maria said Femexfut had informed FIFA and the Gold Cup organisers to open an investigation.
"The cause is believed to be because of (eating) beef or chicken between May 17 and 20 so an investigation will be made with the food suppliers. For the time being we don't see any negligence by anyone, not even theirs," De Maria added.
"We know there is a health alert throughout the country because of food contaminated with clenbuterol and that will be taken into account for the investigation."
Mexico denied in April that its beef contained clenbuterol days after Germany's anti-doping agency (NADA) advised against athletes eating products from Mexico because it might increase the risk of involuntary positive doping results.