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Video - China women win team gymnastics
By Michael Bristow
BBC News, Beijing
The International Olympic Committee has instigated an investigation into the ages of several Chinese gold-medal-winning gymnasts.
China is being asked to hand over extra documents to confirm that five gymnasts were old enough to compete.
The BBC has seen one document on the internet that suggests gold medal winner He Kexin is only 14 years old, not 16 as the rules require.
Chinese officials have strenuously denied the allegations.
If true, they would tarnish the home nation's image.
For several months, there have been rumours about the ages of a number of Chinese gymnasts.
The International Gymnastics Federation confirmed it was looking into the cases of Miss He, Yang Yilin, Jiang Yuyuan, Li Shanshan and Deng Linlin.
All five were awarded gold medals at this Olympics, as part of the Chinese female squad that won the women's team event.
He Kexin won two Olympic gold medals
The BBC has seen an internet document apparently from the website of China's General Administration of Sport, dated last year.
It lists China's gymnasts and records He Kexin's birthday as 1 January, 1994 - that would mean she is only 14.
But on the Beijing games official website, Miss He's birthday is given as 1 January, 1992, which would mean she is 16.
The age issue has already been investigated twice by the IOC, in the spring of this year and just before the games began.
But on Friday, IOC spokeswoman Giselle Davies said: "We have asked the gymnastics federation to look into what have been quite a number of questions and apparent discrepancies on this case."
Ms Davies said she was confident that the gymnasts did meet Olympic age requirements. China was even more confident. Wang Wei, executive vice-president of the Beijing organising committee, said an investigation had already been held into the matter.
"If they had not been cleared, they would not have participated in the games," he said at a press conference.
Lu Shanzhen, chief coach of China's women's gymnastics team, told the BBC that "relevant documents" belonging to He had been given to the IOC and the International Gymnastics Federation yesterday.
The items, including an old passport, a residency card and her current identity card, were issued by various departments of the Chinese government.
"It's only because there is a rivalry between the Chinese and American women's gymnastics teams that these questions have arisen," Mr Lu said.
The United States came second to China in the women's team event.
Mr Lu also told reporters that the parents of the gymnasts were "indignant" over persistent questions about their daughters' ages.
"They have faced groundless suspicion. Why aren't they believed? Why are their children suspected? Their parents are very angry," he said.
"It is in the interests of all concerned, not least the athletes themselves, to resolve this issue once and for all," said the International Gymnastics Federation later in a statement.
The age rule was introduced in 1997 to protect the health of young gymnasts.