(CNN) -- American judoka Nicholas Delpopolo has been thrown out of the Olympics after a failed drug test he blamed on inadvertently eating food that had been baked with marijuana.
The 23-year-old has been disqualified from the 73-kilogram class competition by the International Olympic Committee, after finishing seventh.
Delpopolo is the first athlete at the 2012 Games to fail an in-competition drug test and in a statement released by the United States Olympic Committee (USOC) he said he was embarrassed by his mistake.
"My positive test was caused by my inadvertent consumption of food that I did not realize had been baked with marijuana, before I left for the Olympic Games," Delpopolo said.
"I apologize to U.S. Olympic Committee, to my teammates, and to my fans, and I am embarrassed by this mistake. I look forward to representing my country in the future, and will rededicate myself to being the best judo athlete that I can be."
Delpopolo won his opening bouts against fighters from Hong Kong and Belgium before defeats to South Korea and Mongolia put him out of medal contention.
He was tested on July 30 -- the day of his competition -- and accepted his disqualification after admitting the offense.
"Nick Delpopolo has failed an in-competition drug test (THC, marijuana) and as a result, he has been disqualified from the Olympic Games by the International Olympic Committee," a statement from the USOC said.
"The United States Olympic Committee is absolutely committed to clean competition and stringent anti-doping penalties.
"Any positive test, for any banned substance, comes with the appropriate consequences and we absolutely support the disqualification."
Italy's Olympic 50km race walk champion Alex Schwazer is also out of the Games after failing a drugs test.
Schwazer broke the Olympic record in Beijing when he stormed to gold but will not travel to London to defend his title. The Italian Olympic Committee confirmed on their website they had excluded an athlete for doping.
Italian news agency ANSA quoted Schwazer as saying: "My career is finished. I wanted to be stronger for this Olympics, I made a mistake."
Elsewhere, Algerian middle distance runner Taoufik Makhloufi has been reinstated to the men's 1,500 meters final after initially being disqualified for not trying hard enough in his 800m heat.
Makhloufi won his 1,500m semifinal on Sunday but Algeria did not remove him from the 800m heats before the required deadline.
The 24-year-old completed just 200m of his heat before retiring, prompting the International Association of Athletics Federations (IAAF) to release a statement that appeared to eject him from the Games.
"The referee considered that he had not provided a bona fide effort and decided to exclude him from participation in all further events in the competition," the statement read.
But the IAAF later said Makhloufi had been reinstated and would take his place in the final.
Meanwhile, a 34-year-old man has denied throwing a bottle onto the track prior to the start of the men's 100m final in the Olympic Stadium on Sunday, according to the UK Press Association.
Ashley Gill-Webb pleaded not guilty at Stratford Magistrates' Court to a public order offense after he was taken from the stadium by security staff.
Dutch judo competitor Edith Bosch was nearby and posted on her Twitter site: "A drunk guy threw a bottle on the track in front of me -- I hit him.... Unbelievable!"