Athletics Integrity Unit (AIU) banned Moroccan marathon runner El Mahjoub Dazza for four years after testing positive for violating anti-doping rules.
AIU investigation found anomalies in his Athlete Biological Passport (ABP).
Dazza set a national record of 2 hours 5min 26sec at the Valencia Marathon in 2018. He also won the Prague Marathon and Fukuoka Marathon last year.
The fundamental principle of the Athlete Biological Passport (ABP) is to monitor selected biological variables over time that indirectly reveal the effects of doping rather than attempting to detect the doping substance or method itself.