Samples from the 2017 Tour de France are being re-tested as authorities look for a previously undetectable performance-enhancing substance, Belgian newspaper Het Nieuwsblad reported on Saturday.

REUTERS: Samples from the 2017 Tour de France are being re-tested as authorities look for a previously undetectable performance-enhancing substance, Belgian newspaper Het Nieuwsblad reported on Saturday.

"On the basis of additional information... we have identified the relevant samples and carried out the first analyses," a spokesperson for the Cycling Anti-Doping Foundation (CADF) was quoted as saying by Het Nieuwsblad.