The international equestrian body, the FEI, has been informed that the “B” sample of Waterford Crystal was stolen in Cambridgeshire last month.
Waterford Crystal was ridden by Cian O'Connor in his gold medal victory at the Athens Olympics in August.
The sample was being transported to Cambridge from Paris when it was taken on 21 October. Police in Cambridge have opened an investigation into the incident.
Mr O'Connor has repeatedly denied he is guilty of any wrongdoing with regard to the positive test for banned substances concerning Waterford Crystal.
