Olympic hammer champion Dilshod Nazarov has been temporarily suspended after one of his samples failed a doping retest.
The 37-year-old won Tajikistan’s only gold medal at Rio 2016.
But the Athletics Integrity Unit (AIU) confirmed that a sample from the 2011 World Athletics Championships tested positive for the steroid turinabol.
Nazarov finished 10th in Daegu in 2011 before claiming his only world medal with silver in Beijing in 2015.
He will miss out on an eighth World Championships appearance in Doha, which starts on Friday.