Jemima Sumgong has been suspended for four years for doping.
The Kenyan Olympic marathon champion was banned after the blood booster EPO was found in her system following an out-of-competition test in her home country.
The 32-year-old has previously tested positive for a banned substance in 2012.
Sumgong won the London Marathon in 2016 before claiming gold in Rio, becoming the first Kenyan woman to take the title.
Between 2011 and 2016, more than 40 Kenyan track-and-field athletes failed doping tests.
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