RIO DE JANEIRO - Veteran Fluminense midfielder Deco was seeking to clear his name on Tuesday after it emerged he tested positive to a banned substance.

The 35-year-old former Portugal international was found to have traces of the masking agent furosemide in test samples given after Fluminense's 2-0 victory over Boavista in Brazil's Campeonato Carioca on March 30, Lancenet reported.

"His major concern is to protect his image and not with any punishment that may be handed to him," Deco's advisor Acaz Felleger said on Tuesday.

"He has been taking a vitamin supplement for a long time and it seems like there was some kind of contamination. He is talking with his lawyers about taking possible legal action against the pharmacy."

Deco has been left out of Fluminense's squad for Thursday's Copa Libertadores round of 16 first leg against Emelec in the Ecuadorian city of Guayaquil.

Furosemide is a diuretic that acts by inhibiting the kidneys' ability to retain water and is banned due to its effectiveness in hiding other prohibited substances.

Deco has reportedly requested a secondary test, which is understood to be scheduled for April 3.

The former Porto, Barcelona and Chelsea star has helped Fluminense to two Brazilian Serie A titles since joining the club in 2010.