American judo fighter Nick Delpopolo was expelled from the Olympics on Monday after testing positive for marijuana he said he ate accidentally before arriving in London.

Delpopolo is the first of the 10,500 Games' athletes to fail an in-competition doping test.

His case is the fifth positive test for a banned substance reported by the IOC since its official London Games testing period began in mid-July.

The other four athletes were caught before competing.

The International Olympic Committee said it disqualified Delpopolo from the men's 73-kilogram class, where he placed seventh. Delpopolo tested positive for metabolites of cannabis after competing on July 30.

He apologized to the United States team in a statement acknowledging he was "embarrassed by this mistake."

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