Five riders have been provisionally suspended by the International Equestrian Federation (FEI) after their respective horses tested positive for banned substances.
The Indian trio of Sarvesh Singh Pal, Apurva Dabhade and Raj Kumar, along with Argentina's Daiana Chopita and Waad Nadim Bou Moghlbay of the United Arab Emirates, have all been given provisional bans by the worldwide governing body.
Chopita has been sanctioned for two separate breaches of the FEI's anti-doping rules.
A sample provided by Chopita's horse J C Cahuel returned a positive test for trometamol at an endurance competition in Abu Dhabi on November 9.
Another horse ridden by Chopita, HLP Gadafi, tested positive for the substance at an event in the same city the following month, held on December 23.
Moghlbay's horse, JLB Noche, also failed for trometamol in Abu Dhabi.
Singh Pal, Dabhade and Kumar were banned after their horses failed drugs tests following an eventing competition in New Delhi on November 9.
The horses involved have all been suspended for two months, while the length of the provisional bans for the athletes has not yet been confirmed.
Each case has now been deferred to the FEI Tribunal for a final decision.
"The athletes have been provisionally suspended from the date of notification until the FEI Tribunal renders its decisions," a statement from the FEI on the cases read.
The suspensions mark the latest drug-related offences to hit the sport and dozens of horses and riders have now been suspended for positive tests.