Kim Jong Su, a North Korean pistol shooter, was stripped of his two medals and expelled from the Games after testing positive for the betablocker Propanolol, which can prevent shaking.
A Vietnamese gymnast, Thi Ngan Thuong Do, who finished in last place in the women’s floor exercise, tested positive for the diuretic furosemide.
Prof Arne Ljungqvist, chairman of the International Olympic Committee’s medical commission, said he believed Kim had deliberately taken the drug.
“I cannot interpret the finding in any other way than it was deliberate,” he said. “It is banned in precision sports such as shooting and archery.”
Meanwhile, Ethiopia’s Tirunesh Dibaba decimated the Olympic women’s 10,000 metres record to take gold ahead of Elvan Abeylegesse. Dibaba produced a stunning sub-60 second last lap to smash the previous mark set by her cousin Derartu Tulu in the 2000 Sydney Games with a time of 29 minutes 54.66 seconds.
Dibaba’s 25-lap head-to-head battle with Turkey’s Abeylegesse erupted five-and-a-half laps from home and continued to the bell before she produced her astonishing finish.
However, Ethiopia-born Abeylegesse didn’t let Dibaba have it all her own way as she smashed Paula Radcliffe’s European record with a time of 29:54.66.
Shalane Flanagan lowered her US record to 30:22.22 to claim the bronze medal.
Dibaba now plans on becoming the first woman to claim the 5,000m and 10,000m Olympic double next week.
Tomasz Majewski sprung a surprise as he claimed shot putt gold in an event that was expected to produce an American clean sweep of the medals.
The Pole showed a personal best in the qualifying round of 21.04 metres was no fluke when raising it to 21.51m to cause a huge upset.
Christian Cantwell rallied in the last round to steal the silver medal for the USA with a throw of 21.09m, ahead of Belarus’ Andrei Mikhnevich.
World-record holder Usain Bolt hinted he was the man to beat in the 100m as he coasted to an effortless victory in his heat in a time of 9.92. The Jamaican flew through 50 metres before easing down and jogging across the line well clear of his rivals.
“I just ran the first 50m then I looked around to make sure I was safe and I shut it off,” said the 21-year-old, barely out of breath.
“I’m ready for my best. I think I did well – I got my stride back.”
Tyson Gay, running for the first time in six weeks after recovering from a hamstring injury, definitely lacked sharpness when finishing behind Richard Thompson in a time of 10.09.
“I felt pretty good, pretty relaxed and I just wanted to make it through,” insisted Gay. Asafa Powell who lost his world record to fellow countryman Bolt at the end of May, looked comfortable when coasting to victory in a time of 10.02sec.
Meanwhile Spain's Rafael Nadal underlined his dominance of men's tennis with a three-set win over Novak Djokovic to reach the Olympic Games final.
Nadal, who will face Chile's Fernando Gonzalez tomorrow, overcame a second-set lapse to win 6-4, 1-6, 6-4 in two hours and 10 minutes.
Nadal, who becomes world number one the day after the final, is now just one match away from adding the gold medal to this season's seven-trophy haul including the French Open and Wimbledon.
“For me it's a dream have be in this final,” he said. “Today was very important. Even if I lose the final I'll have one medal for me and for my country.’’