Colombia's Diego Palomeque has been given a temporary ban from the Olympics after failing a drugs test.
The 400m runner was expected to compete in his event's heats on Saturday morning but the International Olympic Committee has moved quickly to expel him from the Games.
Palomeque provided a urine sample in London on July 26 that was found to have excess testosterone in it.
The 18-year-old was not given the opportunity to provide a 'B' sample by the IOC and now faces a two-year ban if found guilty of the offence.
