American endurance rider Nicki Meuten has been provisionally suspended by the International Equestrian Federation (FEI) after her horse failed a drugs test.
FYF Dutch tested positive for O-Desmethyl Venlafaxine, an antidepressant banned under the FEI's anti-doping rules.
The horse failed at an event in Coates Creek in Canada on July 2 of this year.
Meuten's provisional suspension kicked in from October 16, the date she was notified.
The FEI Tribunal will now consider the case and make a final decision, which can be appealed.
A two-month suspension has also been issued to FYF Dutch.
Endurance World reports that Meuten won her race in Coates Creek over 160 kilometres, and collected the "Best Condition" award.
She came home in front of fellow American Holly Corcoran and Canadian Wendy MacCoubrey respectively.
According to the FEI's website, Meuten, who is 47, is ranked 339th in the world in the FEI's Open Riders World Endurance Rankings.
Earlier this month, the FEI signed a deal with Boehringer Ingelheim, a global pharmaceutical company and the world's biggest equine health business, to promote horse health and education.