Indian women's discus thrower Neelam Singh, positive for doping at the Helsinki world championships, said on Monday her urine sample may have been contaminated.
"I do not rule out the possibility of a possible contamination," she read out from a prepared statement at a news conference.
Singh, the 2002 Asian Games champion, tested positive for the prohibited stimulant pemoline during competition at the championships in Helsinki which ended on Sunday.
The 34-year-old, facing a two-year ban from competition, has been provisionally suspended pending a hearing by the Indian federation.
One of India's top athletes for many years, Singh managed only 56.70 metres to be eliminated in the preliminary round in Finland. Her personal best is 64.55 metres in 2002.
"I don't know from where the said substance has come into my sample...I'm innocent and I will do everything to prove my innocence," she said.
Singh, with coach and husband Jaswant by her side, said she suffered from asthma and had provided a list of supplements and vitamins to the International Association of Athletics Federations (IAAF) on August 7, the day she was tested.
The incident has been splashed on the front pages in the Indian media, coming a year after the nation was shamed when two women lifters were caught for doping at the Athens Olympics.