Jamaica's women sprinters bungled their relay race on Friday to hand gold to Russia [Images] and snuff out the Caribbean island's chance of winning all athletic speed events at the Olympics [Images].

Jamaica had won all four individual speed golds in a dominating performance on the track, led by the dazzling Usain 'lightning' Bolt.

They have eclipsed the United States, the traditional track superpower, and embarrassing baton drops by the US teams in both the men's and women's 100m heats had made the Jamaicans firm favorites for two more golds.

That was until Sherone Simpson failed to get the baton across to Kerron Stewart, the woman she shared the 100m silver medal with, and the Russian sprinters seized their chance.

Some redemption should come later when double gold medalist and world record breaker Bolt runs the third leg in the men's relay, handing over to former world record holder Asafa Powell [Images].

Ethiopia's Tirunesh Dibaba stormed to victory in the 5,000m, becoming the first woman to win both long distance races at the same Olympics. She won the 10,000m a week ago in the second fastest time recorded.

Her great rival and compatriot Meseret Defar was pushed into third by Ethiopian-born Elvan Abeylegesse, who runs for Turkey, who also won silver in the 10,000m.

The anticipated dominance of long distance track running by the Ethiopians should be continued by 10,000m gold medalist Kenenisa Bekele who is aiming for the double in the men's events. The 5,000m is on Saturday, the last full day of competition.

AGE QUESTIONS

China have barely featured in the track events, where they have hoped to score some success to match their medal dominance in sports like table tennis and diving.

Big hope, 110m hurdler Liu Xiang, pulled out of his heat with injury, devastating legions of Chinese fans who had prayed for a repeat of his 2004 win, the country's first track gold.

Concerns have resurfaced over how far China have been prepared to go to deliver a Games of which the Chinese can be proud.

The International Olympic Committee has ordered an investigation into allegations Chinese authorities falsified the age of a double gold medal winning gymnast because she was too young to compete.

China's He Kexin, who won team gold in artistic gymnastics and an individual title on the asymmetric bars, was registered as being born on January 1, 1992, meeting the rule that gymnasts must at least turn 16 in the year of the Olympics.

There have been persistent media allegations He competed in earlier tournaments under a later birth date. On Thursday an American computer expert said he had uncovered Chinese state documents that proved she was 14 and not 16.

The caption on a photograph published by Chinese state news agency Xinhua last year referred to "13-year-old He Kexin", while China Daily reported in May that she was 14.

An IOC official said the gymnastics federation would look into "discrepancies" over He's age but Games organizers were at pains to stress she had already been cleared to compete.

"Everything that has been received so far shows we have no problem of eligibility for these competitors," said the IOC's sports director Christophe Dubi.

The age rule was introduced in 1997 to protect gymnast's health, and China's gymnastics coach told a news conference all the team "were in total compliance with the age requirement".

"Since Asian bodies are not the same as Westerners', there have been questions, but there shouldn't be," Chinese head coach Huang Yubin said. A finding is likely to come well after the Games end on Sunday and the intense media focus moves elsewhere.

The eight golds of swimmer Michael Phelps [Images], Bolt's superb sprinting and China's dominance of the medal table have been the stories of the Games.

China now have 46 golds to the 30 won by America. The Chinese say this shows they now have the sporting prowess to match their rising superpower status.

THRILLS AND SPILLS

There were thrills and spills on the BMX track on Friday as the Games' youngest competition produced a thrilling finale.

The BMX competition was introduced at these Games to attract a younger audience. France's [Images] Anne-Caroline Chausson won the women's gold after a tight race with Britain's Shanaze Reade, who crashed on the final bend as she tried to regain the lead.

The dreadful week for the American sprinters, in which they failed to win gold for the first time since 1976, prompted a post mortem from the "extremely disappointed" chief of US athletics.

"These are professional athletes who are the best in their field and anybody who ever ran a high school relay cringes when that baton hits the track," Doug Logan said.

The United States, top of the medals table at the last three Summer Olympics, notched up their 30th gold of the Games on Friday in beach volleyball.

Todd Rogers and Phil Dalhausser won the men's event to complete the double for the U.S. team in the sport.

The Americans hope for more golds in the men's and women's basketball, with the highly-paid NBA players overwhelming favorites to win the gold they embarrassingly missed in Athens.