Morocco's Mariem Alaoui Selsouli has been provisonally suspended from all competition in athletics after testing positive for the banned diuretic furosemide, the IAAF have confirmed.
Selsouli's sample was collected at a Diamond League meeting in Paris on July 6 and she has waived her right to the B analysis.
Selsouli, the favourite for the women's 1500m gold medal at London 2012, has the right to request a hearing which would need to be held by the Moroccan Athletic Federation within the next three months.
Her suspension was confirmed in an official statement from the athletics governing body.
Selsouli, 28, served a two-year ban from 2009-11 for a doping offence.
Following her past offence, Selsouli could face a lifetime ban if found guilty.
Selsouli won silver at the World Indoor Championships earlier this year but her hopes of Olympic success are now over.
The IAAF have said they will make no further comment on the matter.