Mexico, under a cloud after five players tested positive for doping, completed an unbeaten Group A run in the CONCACAF Gold Cup with a 4-1 victory over Costa Rica on Sunday.

The win, in the shadow of the doping suspensions which it claimed was the result of contaminated food, ensured Mexico advance to the quarterfinals.

Andres Guardado scored twice during a first-half assault that gave Mexico a 4-0 advantage by halftime. Rafael Marquez and Pablo Barrera also scored before the break.

Marcos Urena scored in the 68th minute for Costa Rica, which will also advance to the quarterfinals after finishing tied for second in Group A on four points with El Salvador but has a better goal difference.