BEIJING (AFP) - - Jamaican Usain Bolt streaked to the 200m gold in world record time Wednesday to complete the sprint double for the first time in 24 years at the Olympic Games and then loudly declared himself "Number One".
Bolt's scintillating run in front of 91,000 people in the packed Bird's Nest stadium came four days after his epic record-breaking victory in the 100m final.
It also put the competition back in focus after the Games were stung earlier in the day when it was revealed Ukraine's heptathlon silver medallist Liudmyla Blonska had become the first high-profile doping failure.
On the eve of his 22nd birthday, Bolt bagged the 100m-200m double last achieved by Carl Lewis in 1984, stopping the clock at 19.30sec to shatter Michael Johnson's 12-year old record.
After an impromptu dance on the track, an ecstatic Bolt repeatedly chanted "I am number one" as the crowd responded with a chorus of "Happy Birthday".
"I feel good. I have just proved to the world I am a true champion and with hard work anything is possible," Bolt told BBC television.
Churandy Martina of the Dutch Antilles claimed silver and defending champion Shawn Crawford was promoted to third after team-mate Wallace Spearmon was disqualified for running out of his lane.
Meanwhile the International Olympic Committee confirmed the 30-year-old Blonska had failed her A sample and the result of the B sample would be known Thursday.
Blonska faced a lifetime ban if both samples prove positive after serving a previous suspension for taking stanozolol, the anabolic steriod used by disgraced sprinter Ben Johnson.
International Athletics Federation president Lamine Diack confirmed an investigation was underway.
"The procedure is running. The B-sample will no doubt be opened today and a decision taken tomorrow."
If confirmed, Blonska would be the fifth athlete to test positive, although the previous four only involved one podium finisher - North Korean shooter Kim Jong-Su, a minor medallist.
China continues to hold a commanding lead on the medal table with 45 compared to 26 for the the United States and 16 for Great Britain.
Jamaica also scored a psychological edge over the United States in the women's 200m with Veronica Campbell and Kerron Stewart the fastest qualifiers in the semi-finals ahead of Allyson Felix of the United States.
Cuba's world record holder Dayron Robles continued to look unbeatable as he breezed through the semi-finals of the 110m hurdles, with his path eased by the injury withdrawals of Chinese icon Liu Xiang and American Terrence Trammell.
Ethiopian Kenenisa Bekele, who already has the 10,000m gold, cruised into the final of the 5000m to keep his bid afloat for the double last achieved by compatriot Miruts Yifter in the 1980 Moscow Games.
On another successful day for the Games hosts, sailor Yin Jian won the women's windsurfing and Wu Jingyu beat Thailand's unfancied Buttree Puedpong in the women's -48kg taekwondo.
They also entered their first ever women's hockey final with a thrilling 3-2 win over reigning champions Germany.
At the opposite end of the scale to China's runaway medal success, taekwondo produced emerging Afghanistan's first ever Olympic medal when Rohullah Nikpai took the men's -58kg bronze medal. Guillermo Perez of Mexico won the gold.
Russian open water superstar Larisa Ilchenko entered the record books as the first women's 10km swimming marathon champion when the sport made its debut on Wednesday.
South Africa's Natalie du Toit, created a record as the first amputee to qualify for the Olympic Games, finished 16th in the 25-strong field women's swimming marathon and pledged to be back in 2012 to do better.
"I don't even think about not having a leg and if I want to keep competing I will have to continue to qualify with the able-bodied. For me it's not about the disability at all," said du Toit who lost her left leg in a motorcycle accident seven years ago.
