Kylie Palmer has withdrawn from the Australian swimming team for the upcoming FINA World Championships after being provisionally suspended for an alleged doping offence.

Palmer tested positive to a minute trace of a prohibited substance at the World Championships in Barcelona nearly two years ago, and was notified of the breach in April this year, Swimming Australia said in a statement on Thursday.

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The 25-year-old has maintained she has no idea how the unnamed substance came into her system and categorically denies knowingly taking any prohibited substance in Barcelona in July 2013, or at any time in her career.

Palmer won a gold medal at the 2008 Beijing Olympics as part of the 4x200m women’s relay team.