Brazil's world champion gymnast Daiane dos Santos, preparing for training last year, has tested positive for doping. Brazil's world champion gymnast Daiane dos Santos, preparing for training last year, has tested positive for doping. (Andre Penner/Associated Press)

Former world champion gymnast Daiane dos Santos has tested positive for the drug furosemide during a non-competition doping control.

The International Gymnastics Federation says on its website that Santos, the floor exercise world champion in 2003, had knee surgery this year and could have been given the drug by mistake. She tested positive in July.

Furosemide, a weight-loss drug, can be used as a masking agent for other banned substances.

Calls to Brazil's national gymnastics federation and Santos' home club were not immediately returned.

Santos, who could be barred for two years, has until Nov. 13 to present a defence to the federation.