Some of China's Olympic gymnasts could lose their medals in a row over whether they were old enough to compete.
All gymnasts have to be at least 16 years old in the same year as the Games take place, but it's being claimed that a few of them may only be 14 years old.
There are reports that an official Chinese gymnastics website used to say five of the gymnasts were younger than Chinese officials say they are now.
But the officials insist they have lots of documents proving they are all 16.
The International Olympic Committee (IOC), who organise the Olympics, says it has checked the passports of all the gymnasts and they're all OK.
Beth Tweddle could grab a medal if it's proved that He is too young
Even so, because so many people have been asking questions, the IOC has told gymnastics bosses to double-check the gymnasts' ages.
Some Chinese officials have said people think their gymnasts are too young because they are smaller than those born in other parts of the world.
One of the gymnasts, He Kexin, has so far won two gold medals at the Olympics, including one for the uneven bars in which Britain's Beth Tweddle finished fourth.
So, if He is found to be too young and gets kicked out of the Games, Beth could yet win a medal.
An age limit on gymnasts was brought in to try to stop them getting injured.
It's thought younger gymnasts are more flexible, so they find it easier to complete the tumbles and twists needed.