Olympic and world 5000 metres silver medallist Ali Saidi-Sief of Algeria tested positive for the banned drug nandrolone at the Edmonton world championships, according to the International Association of Athletics Federations (IAAF).
Saidi-Sief now faces a possible two-year ban and could be stripped of the silver medal he won at last week's world championships where the test took place.
If Saidi-Sief is disqualified his silver medal will go to Ethiopia's Million Wolde, who finished third while fourth place finisher John Kibowen will be awarded the bronze.
The race was won by Kenyan Richard Limo, who produced a kicked past Saidi-Sief on the final bend and sprinted down the home straight to win in 13 minutes 0.77 seconds.
Saidi-Sief, who had been beaten by a late burst by Wolde at last year's Sydney Olympics, finished in 13:02.16 while Wolde took the bronze medal in 13:03.47.
The Algerian was supposed to race against Limo in the 5000m at Friday night's Golden League event in Zurich but pulled out on Thursday, citing family reasons.
Limo won the event on Friday on a time of 12:56.72