"A total of 105 riders have been tested and 16 samples from 13 athletes have tested positive," Pierre Bordry, the head of the French anti-doping agency (CPLD), said in an inteview to be released in daily Le Monde later on Friday.
"Floyd Landis's case put aside, the International Cycling Union (UCI) has closed the cases arguing all the riders had a TUE."
"This is not a surprise because it is UCI that decided to give these TUE. What is worrying is that 60 per cent of the tested riders have said they had a TUE."
The Therapeutic Use Exemption allows an athlete to take a banned substance to treat a medical condition such as asthma.