Olympic history is being rewritten thanks to the International Olympic Committee's (IOC) practice of retesting urine samples taken from athletes at the 2008 and 2012 Olympic Games.
The IOC, which stores samples for 10 years, has reanalysed more than 1,000 samples from the Beijing and London Olympics with improved techniques that can detect the use of steroids going back weeks and months, rather than days.
Of the 98 samples which have come back as positive so far 49 belonged to athletes who were awarded medals at those games.
HOW THE PROCESS WORKS
By the end of any Olympics, IOC testers are in control of as many as 5,000 urine samples.