Although the Argentinian football federation's anti-drug commission declined to say what illegal substances had been found, Maurico Macri, president of Boca Juniors, said he had been told traces of cocaine were present in the urine sample. He said a ban of up to three years seemed likely if this was confirmed, adding: "Maradona has failed himself more than the Boca team."
Maradona, paid $50,000 (pounds 32,000) per match by Boca, has a clause in his contract which stipulates that he must undergo a private doping test before every game. He said that his club test on Sunday had proved negative, although he tested positive after the game. His manager Guillermo Coppola, himself jailed on cocaine charges last year, said he did not believe his friend had taken drugs before the match. "There must have been some mistake," he said.
Maradona, who led Argentina to the 1986 World Cup, signed for Boca Juniors for the third time in April. He had spent the last year training in Canada with the sprinter Ben Johnson, who was banned for life for illegal drug use.
Maradona, 36, has previously admitted using cocaine. In 1991, while playing in Italy for Napoli, he was banned for 15 months after testing positive for the drug. Later that year he was arrested in Buenos Aires and charged with drug possession and trafficking. He was given a 12-month suspended sentence.
Fifa, the sport's world governing, then banned him for 15 months after he tested positive for five prohibited stimulants at the 1994 World Cup finals. He spent several weeks in a Swiss clinic last winter in an attempt to conquer his drug habit and even headed a public anti-drug campaign.