Shane Warne is returning home from the Cricket World Cup after testing positive for a banned substance.
Warne faces the media in Johannesburg
The Australian Cricket Board (ACB) said the star leg-spinner had tested positive for the drugs hydrochlorothiazide and amiloride.
They are both diuretics normally used to aid temporary weight loss.
But they can also serve as masking agents for performance-enhancing drugs, and that is why they are banned in cricket.
Warne said he was "shocked and devastated" after being told by Australia's Sport Drugs Agency about his failed test.
The 33-year-old said: "I have never taken performance-enhancing drugs, and I do not condone their use."
He had already announced he would retire from the one-day game after the World Cup, and though he wants to continue his Test career, he may not now be allowed to do so.
The people to lose out are the fans because they won't be able to see the best bowler in the world
Matthew Harding, Australian fan in Johannesburg
According to ACB guidelines, Warne faces a mandatory two-year ban from the game if the B sample, which will be tested in the next few weeks, also proves positive.
However there are grounds for the ban to be reduced pending evidence from the ACB's anti-doping medical adviser.
The ACB said the positive test had been triggered by fluid reduction medication, which Warne claimed was not performance-enhancing.
Warne will appear before an ACB Anti-Doping Committee hearing as soon as possible.
He had a made a rapid recovery after disclocating his shoulder in a one-day international against England on 15 December.
One of Wisden's five greatest cricketers of the 20th century, he was man-of-the-match in Australia's World Cup final win over Pakistan in 1999.
Last September, the Aussie star agreed to return to the English county championship with Hampshire on a two-year deal to skipper the side from this summer.
Hampshire chairman Rod Bransgrove was unavailable for comment. He is said to be attempting to contact Warne directly.
Australia will now apply to the International Cricket Council's technical committee to replace Warne in their World Cup squad.
A World Cup spokesman confirmed it was now "possible" for a replacement to be approved.
Australia could choose between two other leg-spinners in New South Wales's Stuart MacGill or the much younger Cameron White of Victoria.
Brad Hogg will take over as the primary spinner in the side from now on after a successful series against England and Sri Lanka.