Botswana’s 2012 Olympic 800m silver medallist Nijel Amos has been suspended by the Athletics Integrity Unit after testing positive for a banned substance.
Amos, 28, was in the US preparing for the World Athletics Championships which begin in Eugene, Oregon, on Friday.
The 2014 Commonwealth Games gold medallist failed an out-of-competition test taken last month.
The sample contained a substance called GW1516, which can boost endurance.
GW1516, a metabolic modulator, was banned for human use in 2007 and is prohibited by the World Anti-Doping Agency (Wada).
Originally developed to treat obesity and diabetes, the drug was found to cause cancer during clinical trials on animals, and was added to Wada’s prohibited list in 2009 after its illicit use as a doping agent emerged.
Amos was due to race in the 800m heats on July 20. – BBC