The women's 1,500 metres Olympic favourite Mariem Alaoui Selsouli has tested positive for a banned diuretic and will miss the London Olympics.
The Moroccan runner, a silver medallist at the world indoor championships this year, has already served a two-year suspension for doping and now faces a lifetime ban under World Anti-Doping Agency rules.
The 28-year-old became the hot favourite to win gold in London when she ran three minutes 56.15 seconds to win the Paris Diamond League at the Stade de France earlier this month.
It was the fastest 1,500 metres time since 2006 and shaved more than four seconds off her personal best, raising question marks that were answered yesterday.
The sample was collected on July 6th and Selsouli has waived her right to the B analysis, and as a result has been provisionally suspended from all competition in athletics.
Diuretics are used to mask the presence of illegal drugs.