Costa Rica officials have sent a letter to FIFA questioning why so many of their squad were required to submit to anti-doping controls following Friday's victory over Italy.
Seven Ticos players underwent regulation tests after the 1-0 victory in Recife, which has left the Central American nations' football association angered.
"We believe in, accept and trust doping controls that FIFA carries out, but we want an explanation as to why so many of the players were called in," president of Costa Rica's selection committee, Adrian Gutierrez, is quoted as saying by ESPN.
"What causes surprise at the world level is that they take seven players in one sitting for anti-doping tests, which gives an image of suspicion that Costa Rican players are doping."
Costa Rica face England in their final Group D game on Tuesday evening.