Swedish 1500metre runner Abeba Aregawi has been provisionally suspended by the Swedish Athletics Federation (SAF) after testing positive for a banned substance.
Aregawi has enjoyed success on the track since switching allegiances from her birth country of Ethiopia in 2012, winning three gold medals and a silver at major championships.
She was crowned world champion in Moscow in 2013, beating previous winner Jennifer Simpson to gold by three tenths of a second.
The 25-year-old failed an out-of-competition test in January and has been suspended with immediate effect.
"Swedish Athletics and IAAF announces that Abeba Aregawi is suspended and is under investigation for suspected doping violation," a SAF statement read.
"When a doping test was done by the IAAF Abeba Aregawi tested positive for a banned substance."
SAF general secretary Stefan Olsson added: "It is with dismay and extreme disappointment we have to make this announcement.
"We are totally opposed to all forms of cheating, doping and illegal means. We have a zero tolerance policy and this is completely unacceptable."