Sprinter Blessing Okagbare is out of the Tokyo Olympics after being suspended for failing a drugs test.
The Nigerian - a rival to Great Britain's Dina Asher-Smith - had won her 100m heat on Friday and was due to race in the semi-finals on Saturday.
The Athletics Integrity Unit (AIU) said the 32-year-old had tested positive for a human growth hormone following an out-of-competition test on 19 July.
The AIU said Okagbare was notified of her provisional suspension on Saturday.
It added it would not be making any further comment at this stage.
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Okagbare, Olympic long jump silver medallist in Beijing in 2008, had posted a time of 11.05 seconds in her 100m heat and was set to line up against Asher-Smith and Jamaica's Elaine Thompson-Herath in the first semi-final.
The news comes two days after 10 other Nigerian athletes were declared ineligible for the Games.
The AIU ruled they were unable to take part because of non-compliance with out-of-competition drug testing requirements in the run-up to the Olympics.
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