Former Chelsea midfielder Deco has failed a doping test in Brazil, with his representative claiming that his vitamin supplement was contaminated.

The ex-Barcelona and Porto star, who is now plying his trade with Fluminense, was tested following his side's clash with Boavista in April, with the results showing that his sample contained furosemide, a banned diuretic that could be implemented to mask other substances.

Fluminense have revealed that they will not make any decisions on a possible punishment until the 35-year-old's 'B' results are released on Friday, while his spokesperson insists that Deco will fight to prove his innocence.

"The first concern for Deco is defending his image and not with any punishment or suspension," Felleger Ahaz told O Globo.

"He has for a long time taken a vitamin supplement and certainly there has been some contamination."

The Portuguese playmaker has been left out of Fluminense's squad for their Copa Libertadores clash with Emelec on Thursday.