Vasco da Gama midfielder Carlos Alberto faces a two-year ban from football after failing a doping test.
The 28-year-old was found to have traces of illegal substances hydrochlorothiazide and metabolic tamoxifen in test samples taken after Vasco de Gama's 3-2 victory over Fluminense on March 2, the Rio de Janeiro Football Federation said on Tuesday.
Hydrochlorothiazide is known as a masking agent while metabolic tamoxifen blocks the production of the female hormone estrogen.
Vasco de Gama said in a statement that the club would contest the charges.
"We are taking all necessary steps to identify the causes and present a defense of the player," the statement said.
The Rio de Janeiro outfit has expressed an interest in extending Alberto's contract, which ends in August this year.